Missoula Avalanche - Weekly Advisories

March 8 Avalanche Advisory

Mon, 08 Mar 2010 00:00:00 MST

Good morning, this is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for March 8, 2010. This is the last regular Monday advisory for the remainder of the season. Friday advisories will be posted, along with updates if warranted, until the end of March.

Current Avalanche Danger
On slopes above 5000 feet and steeper than 35 degrees there is a MODERATE avalanche hazard. On all other terrain in the advisory area the avalanche hazard is LOW.

Weather and Snowpack Analysis
Since Friday's advisory the temperatures have been warm to say the least. The persistent surface slab we have been talking about for the past two weeks has gained strength but continues to react moderately to stability tests and can still be found above 6500' on shaded, cold aspects and on West aspects as well. The sun- drenched South and East slopes pose a problem during the heat of the day. I have posted a photo of a wet slide at lower elevations in the Lolo Pass area at the end of our 2010 folder. This avalanche ran over 300 feet and was large enough to bury someone. This was on a sun-exposed southerly aspect.
Lolo Pass area wet slide 3/6/10
We received an e-mail with this youtube link that shows a slab avalanche triggered by dropping a cornice on 3/6/10. This avalanche on the North side of Morrell Mountain in the Seeley Lake area was sent in from the guys at Yurtski. This demonstrates the previously mentioned persistent slab on the colder aspects. www.youtube.com/user/BackcountryBomb
We are, however, expected to get cold weather and some snow. This could reduce the risk of wet warm slides and further weaken cold aspects.

Weather Forecast and Avalanche Outlook
A cold front is predicted to show up Monday afternoon. The higher elevations could see significant snow over the next couple of days. The Rattlesnakes, Southern Missions and Seeley Lake may see the most precipitation within the advisory area. I would pay close attention to higher elevation slopes that already have weak surface snow (W, NW, N, and NE) for the next few days. We had very strong surface temperature gradients on these aspects during the warm weather. This created surface layers of faceted snow. If we do get 10 to 15 cm of new snow the surface may be unstable immediately.
We definitely want the snow; pay attention to steep slopes on these aspects at elevation if it happens.

Steve will post the next advisory on March 12.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766 (530-9SNO).

March 5 Avalanche Advisory

Fri, 05 Mar 2010 00:00:00 MST

Hello! This is Steve Karkanen with backcountry avalanche information from the West Central Montana Avalanche Center for Friday, March 5, 2010.

Current Avalanche Danger

Above 6000 feet on terrain steeper than 35 degrees, the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible.

Below 6000 feet, the avalanche danger is LOW. Natural and human triggered avalanches are unlikely. We are rapidly losing snow at the lower elevations and 5000 feet is the transition zone from no snow to some snow depending on aspect.

Weekend temperatures are expected to be above freezing even with cloud cover. On slopes exposed to the sun the wet snow avalanche danger will quickly rise to CONSIDERABLE. Human triggered avalanches are probable, natural avalanches are possible. Roller-balls and small point release avalanches are good indicators of an increasingly unstable condition. If you see these indicators or begin punching through the snow to your knees you need to move to a more shaded aspect. Be mindful of what you are exposed to from above.

Weather and Snowpack Analysis

We have been through an extended period of near record breaking warm temperatures with a short cool down Wednesday with minimal precipitation. The weather forecast looks like we go back to warm weather with no precipitation at least through the weekend. These unseasonal warm temperatures have done a lot to wreck the skiing, make the southern exposures nearly isothermal and send all but the die-hard back to town for grassy sports, riding bikes or fishing. A lot of choices these days but come on, there's nothing better than being on the snow when the sun is out, the snow is corn and the view outstanding. And if you know where to look and time it right, the backcountry skiing and riding is still pretty good.

But you have to be careful as we continue to find the buried surface hoar layer we've been describing for the past month to be sensitive in our stability evaluations. This is a widespread condition I think now mostly confined to the more sheltered NW to NE aspects or pockets heavily shaded from the sun. This video gives a good idea of how persistent the problem has been now. Certainly strengthening with the warmer temperatures but still a potential problem worth looking for especially at the higher elevations (7500 feet +).

http://www.youtube.com/watch?v=kNXwthEH3IU

The sun exposed aspects have been warmed to the point where in many areas our observers are finding the snow to be rotten to the ground. With mountain temperatures in the 40's, the southern aspects will be prone to slide in the afternoon hours. They might look OK and are probably just fine in the morning, but during the peak of direct sun or when you start punching through last nights crust, your best course of action is to move to a shaded slope. But don't forget about the buried surface hoar layer we just showed you!

Weather Forecast and Avalanche Outlook

The National Weather Service Office in Missoula is forecasting the weak upper level low pressure system currently over us with isolated snow showers mostly in the southern Bitterroot to move to the east this weekend leaving mostly dry conditions. Saturday and Sunday are expected to be very nice with some clouds lingering over the mountains. The next chance for any appreciable precipitation is early next week.

Expect wet snow avalanche danger to increase during warm afternoons. The stability on northerly aspects will continue to strengthen with the moderate temperatures but don't completely trust anything until you have proven the slope is stable. The variability of our snowpack in Western Montana has been a nagging problem this year. The only slopes you can be 100% sure are safe are those brown grassy hillsides up to the snowline. Above that, pay attention!

If you have not taken the survey, this is your last chance. We plan to take it down and tally the results after Monday March 8. So please take the survey and register for a chance to win a Tracker transceiver, Voille shovel, or a missoulaavalanche tee shirt.

With the current early spring conditions, we plan to issue the final Monday advisory on March 8. This is dependent on weather conditions and we will issue early week advisories as conditions change. We plan to continue with Friday advisories to March 26.

March 1 Avalanche Advisory

Mon, 01 Mar 2010 00:00:00 MST

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Monday, March 1, 2010.

Current Avalanche Danger

Above 6000' on terrain steeper than 35 degrees the avalanche danger is
MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible.

Below 6000 feet, the avalanche danger is LOW, natural and human triggered avalanches are unlikely.

During periods of rapid warming or whenever it begins raining, the avalanche danger will quickly rise to CONSIDERABLE on any slope that has been exposed to the sun. Starting around 10-11am, these aspects have the most potential for wet snow avalanche activity; E to SE to S to SW to W. Under these conditions it is appropriate to retreat to either shaded or lower angle slopes and be mindful of the terrain above you. Any steep slope can quickly become dangerous shortly after it starts raining.

Weather and Snowpack Analysis

Mountain temperatures climbed into the 40's at most SNOTEL sites in the afternoons then dropped back into the teens and lower 20's overnight. Many sites picked up an inch or two of snow which really doesn't matter much. We received reports from skiers in the Wisherd Ridge, Southern Bitterroots and the Rattlesnake areas all reporting low to moderate strength stability test scores associated with the buried surface hoar layer 20-30cm deep. Also the surface snow is undergoing radiation recrystallization (or temperature gradient snow) which is making for some very enjoyable riding but this snow once buried then becomes another layer to be concerned about. No problem today.

We were getting consistent stability test scores that made us a bit nervous. On a NE 35 degree aspect we scored consistent CTM12-14 Q1 failures 35cm deep, an ECTP14 Q1 failure and a Rutschblock 3 Q1. All failing on the buried surface hoar that formed the first part of February. What is noteworthy about this test site is that the snowpack is weaker today than it was Thursday. We opted not to ski this particular slope based on the above info. Other aspects were also showing the buried surface hoar failing with CTM12-14 Q1 30cm deep. South aspects have a nasty sun crust but also fail similarly.

A better illustration of our concern is a close call reported to us last night. The incident occurred on St. Mary's Peak in the Bitterroot. The photos are posted on our photo gallery and the short report is in italics here.

Went out on Saturday to ski at St. Mary's Peak in the Bitteroot. We had a good day out skiing and did not see any recent signs of instability or avalanche activity. However, from previous avalanche reports we knew that serious instability existed in the snowpack just a few days ago. Therefore we used caution and dug a snow pit on an 30 degree NE aspect near the ridge top. Our stability results did not suggest any serious concern, but did break easily on a small layer 10cm deep and provided a hint of what we would see lower down. We ski a NE-E aspect, 30 degree slope and had two good runs until we shifted to a N aspect almost at the bottom of the basin and triggers a small avalanche (size 2) on a slight convex slope (see attached photos). In hind sight it was shocking to see how heterogeneous the quality of the buried surface hoar layer was across the landscape. While we knew areas of instability existed the buried surface hoar layer we encountered was VERY reactive and we should of dug more pits on different aspects to really get a good idea of the stability of the entire cirque. I hope that you can pass this on to other folks. From our experience I would not say that the buried surface hoar layer on N aspects has gained anymore stability since the last avalanche cycle and would suggest people use extreme caution on N aspects.

So the hazard remains and it is certainly enough of a slab to be concerned about and worth looking for when you go out.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting that a ridge of high pressure building over the Northern Rockies will bring drier air and clearing skies through Monday. On Monday the warmest temperatures of the winter are expected with near record highs possible. Moisture moving in ahead of a Pacific low pressure system Tuesday will usher in a cool down that will last into the latter part of the week.

That is a good and bad forecast as it relates to avalanche safety.

Here's why: We have a persistent weak layer that continues to headline our concern. It is now deep enough (30cm) that it could easily injure, bury or kill someone. The cooler temperatures up to this week have not only preserved this layer, but actually made it weaker in many areas. Record breaking high temperatures might be just what it takes to eliminate this problem. But with the high temperatures the probability of wet snow avalanches will increase. Initially these avalanches will involve the snow currently sitting on this 30cm deep layer of buried surface hoar. As the snow melts and water percolates down the first thing it will encounter is the faceted snow and I would expect to see widespread avalanche activity as soon as this happens.

So we need the warm temperatures to stop the faceting process and get this snow to settle and bond but we may go through a period of very unstable conditions to get there.

We've been getting some of the best observations and photographs from skiers and riders we've seen since we started this web site several years ago. Your observations help us produce a more accurate advisory and may save a life. If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766.

February 26 Avalanche Advisory

Fri, 26 Feb 2010 00:00:00 MST

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Friday, February 26, 2010.

Current Avalanche Danger

Above 6000' on terrain steeper than 35 degrees the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible.

Below 6000 feet, the avalanche danger is LOW, natural and human triggered avalanches are unlikely.

At the highest elevations and above tree-line in our mountain ranges, dangerous pockets of unstable snow still exist. Time, warmer weather and very little new snow has settled overall conditions but isolated areas that are very dangerous exist and will remain with us for a few more days. So please remember this: a moderate hazard rating does not mean the danger is gone, just diminished over a broad area. Use this advisory as a starting point. This will give you a good idea of what the potential avalanche problem is and remember we recreate in a dynamic environment where change is constant, over both time and terrain.

Weather and Snowpack Analysis

Mountain weather since Monday has been more of the same (no new snow) with temperatures reaching 45 degrees at Lolo and Lookout passes Tuesday with other SNOTEL locations all reporting temperatures in the high 30's. Cloud cover moved in and it started snowing early Thursday but we were only able to squeeze a couple of inches of snow from it. Lookout Pass picked up the most with 4 inches in the past 24 hours.

The wind probably did more to improve skiing conditions at 8000 feet as wind speeds have been in the 15-30 mph range for the duration of the week starting out from the NW on Monday and slowly working around the W half of the compass to a strong S-SW flow Tuesday, then back again to a W-NW flow Thursday. Elevations below 7500-8000 feet did not seem to be affected by these strong winds.

We have not received any reports of triggered or natural avalanches since Saturday and all observers reported stronger stability tests but all failures involve the buried surface hoar we've been describing for 3 weeks now. On average, it is 25-30cm deep (deeper at higher elevations or near ridge tops on wind loaded slopes) and can be found on all aspects including elevations near the passes. The problem with this particular layer is that it is well protected from the warmer temperatures and will persist as a potential problem whenever we see new snowfall or wind.

It's easy to find by digging a quick pit no deeper than 2 feet down. It will show up as a thin stripe in the pit wall. Poke your fist and fingers into the pit wall to see the differences in strength. With a thin, weak and highly variable snowpack this season and several close calls last week, you need to become more of an investigator than a robber or you stand a good chance of getting caught by the goods themselves.

Your riding or skiing partners might think you're some new kind of freak but they will be impressed when the snow pulls out from under one of them and you say "I told you it was weak"!

Weather Forecast and Avalanche Outlook

An upper level ridge is moving through the northern Rockies today allowing a more southerly air flow that will bring very mild temperatures to the area through Saturday. Very little precipitation is expected until sometime next week.

Expect conditions to slowly improve with the moderate temperatures. The next storm cycle will be potentially very dangerous if it comes in quick, warm and with a lot of precipitation. If the clouds break and we have direct sun on the slope, conditions can rapidly become unstable. Get off and out from underneath any steep open slope. Move to a shaded slope or just stick to the groomers on the ski areas.

The past 2 weeks have been edgy in many areas and we've been getting some of the best observations and photographs from skiers and riders we've seen since we started this web site several years ago. Your observations help us produce a more accurate advisory and may save a life. If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

February 22, 2010 Avalanche Advisory

Mon, 22 Feb 2010 00:00:00 MST

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Monday, February 22, 2010.

Current Avalanche Danger

Above 6000 feet on all terrain steeper than 35 degrees the avalanche danger is CONSIDERABLE, natural avalanches are possible and human triggered avalanches probable.

On other slopes the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. Below 6000 feet, the avalanche danger is LOW, natural and human triggered avalanches are unlikely.

Be especially vigilant during periods of rapid warming. Many wet snow point release avalanches occur during periods when the sun bakes a slope for a few minutes. While these smaller avalanches by themselves do not present much of a hazard, it is possible the rapid load to a weak snow structure can result in these slides stepping down to weaker layers within the snowpack.

Weather and Snowpack Analysis

Cool temperatures have allowed the buried surface hoar layers to persist and in some cases, grow larger. We continue to receive excellent reports from backcountry travelers who have either triggered avalanches or have seen recent avalanche activity. The most recent report was from a group who triggered an avalanche on a north facing slope near St. Mary's Peak Saturday.

In the Rattlesnake Sunday our stability tests were consistent on all aspects with moderate range compression test scores but high quality fast clean energetic shear planes failing at the buried surface hoar about 25cm deep (CTM11, Q1). South and West aspects appear to be the most sensitive and are showing the ability to propagate fractures over distance (ECTP11 25cm deep). Wind loaded terrain may be especially troublesome especially in the higher terrain in the Bitterroot Mountains. Observations from the northern Bitterroots near Hoodoo Pass and further south near Lost Horse at elevations above 7000 feet show similar instability but a much deeper (40cm) slab.

Lower elevation sites such as Lolo and Lookout Passes have a much more stable snowpack and the surface hoar that is troublesome at most other sites was mostly destroyed by warmer temperatures prior to last week's snow. The only way to know for sure is to dig down into the snow a couple of feet to see if it exists. The surface hoar crystals are well preserved and large so they won't be hard to miss in a quick pit.

We watched many people ski 30-35 degree and some steeper terrain without incident so conditions are slowly improving over what we experienced a week ago.

Weather Forecast and Avalanche Outlook

The upper level pattern will transition from a northerly flow to a ridge Monday night and Tuesday. The air mass will be dry with mostly clear skies. Night time and early morning temperatures will be cold due to radiational cooling. Temperatures will begin to slowly warm in the higher elevations as an inversion sets up keeping valley temperatures cool. By Wednesday, most forecast models indicate a breakdown of the high pressure ridge with a moist westerly flow moving into western Montana.

The cooler temperatures will allow the weak layers to persist and the cold clear nights will allow a new layer of surface facets to start growing. Expect conditions to slowly improve as temperatures moderate. The next storm cycle will be potentially very dangerous if it comes in quick, warm and with a lot of precipitation.

Please take the time to fill out our survey. This is your opportunity to let us know what you think the strengths and weaknesses of our program are and where we need to go in the future. Your comments do make a difference.

Avalanche Center Survey

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

February 19, 2010 Avalanche Advisory

Fri, 19 Feb 2010 00:00:00 MST

Good morning, this is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for February 19, 2010.

Current Avalanche Danger
On slopes above 6000 feet and steeper than 35 degrees there is a CONSIDERABLE avalanche hazard. Natural avalanches are possible, human triggered avalanches are probable. On other steep terrain above 5000 feet there is a MODERATE avalanche hazard. Human triggered avalanches are possible. On remaining terrain within the advisory area the avalanche hazard is LOW.

Weather and Snowpack Analysis
The slab I reported about Monday is still with us. I toured the Rattlesnakes today and had unstable results with my stability tests on four different aspects. Tim traveled into the Brushy Fork area of Lolo Creek and found the same conditions. We received a report from the Downing Mountain Lodge near Hamilton that the snow was failing easily on the buried surface hoar as well. Since Monday morning the region received a bit more snow and the slab is anywhere from 12 inches to 20 inches thick across the area. We had surface hoar develop across the region in late January and early February. We haven't gained much snow since then; but what we have gained is sitting on top of this well preserved surface hoar. This layer should be scrutinized for the foreseeable future; particularly above 6000 feet and on slopes with Northerly aspects.
Tim was able to safely ski cut an avalanche in the Brushy Fork that propagated 200 feet across the slope and ran 150 feet into a terrain trap.
I have posted photos of the surface hoar layer in the Rattlesnakes and the slab avalanche in the Brushy Fork on our photo gallery. You can find them at the end of the 2010 season folder.

Weather Forecast and Avalanche Outlook
A Northerly flow is expected to continue through the weekend with slight cooling and modest precipitation, if any. I would look for conditions to stay the same for a few days, particularly on Northern exposures where the snow will remain cold at elevation. For the time being, approach all steep slopes at elevation with suspicion.

Notes from President's day Weekend
This past weekend I know of two well seasoned, cagey backcountry skiers who separately triggered avalanches, were caught, and fortunately came through unscathed. The story is all too familiar for one of them. Obvious clues were there, the settling, the cracking and yet with the lure of a virgin powder run somehow things looked safe. None of us are impervious to the "human factor". We received a comment that someone pre-judged conditions to be stable when the Feb. 12 advisory rated the hazard as MODERATE. First of all, a MODERATE rating does not say conditions are stable; it says human triggered avalanches are possible and there are dangerous conditions in certain terrain features. Even a LOW rating indicates "mostly" safe conditions. And due to the capricious element of snow and weather, hazard ratings must expire by midnight of the day issued. The information contained can provide valuable information for further investigation however.
Do not forego safe travel habits because of perceived stability.
Secondly, do not put all your eggs in one basket, constantly seek information. Do not rely on any one thing; whether that is a snow pit, lack of obvious clues or an avalanche advisory. Endeavor to put the whole picture together.

Education
I will be instructing an avalanche awareness class, along with Lost Trail Ski Patrol members and instructors from missoulaavalanche.org, in Hamilton and Lost Trail Pass this weekend. There is an evening session tonight at 6pm in Conference Room B at Marcus Daly Hospital and a field session Saturday at Lost Trail Pass Ski Area. The class is co-sponsored with the Lost Trail Pass Ski Patrol. You can find more info on the education link on missoulaavalanche.org. $20 donation.

Steve will post the next advisory on February 22.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766 (530-9SNO).

President's Day 2010 Avalanche Advisory

Mon, 15 Feb 2010 00:00:00 MST

Good morning, this is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for President's Day, 2010.

Current Avalanche Danger
On slopes above 6000 feet and steeper than 35 degrees there is a CONSIDERABLE avalanche hazard. On other steep terrain above 5000 feet there is a MODERATE avalanche hazard. On remaining terrain within the advisory area the avalanche hazard is LOW. Normal caution is always advised; you should be increasingly cautious during CONSIDERABLE hazard.

Weather and Snowpack Analysis
We received reports and photos of slab avalanches from across the advisory area. The slab is propagating on the late January surface hoar and is anywhere from 20 inches (Mission Mountains) to 10 inches (Rattlesnakes) deep.
Tim Laroche and I traveled in the Rattlesnakes yesterday to check out a report of a skier-triggered slide. We checked out that slide and observed three other slab avalanches that appeared to have run on Saturday (2/13/10) as well. All of these three avalanches were in a steep East-facing bowl; at least one of them appeared to be skier-triggered. As to the first avalanche we were looking for the YouTube video will give you most of the story. I did a quick stability test in the crown which showed the surface snow was still very weak and failing on the late January surface hoar. And, as Tim reports in the video, we ski cut some of the remaining slab and got it to go way too easily.

http://www.youtube.com/watch?v=_AoN_-6ZG9M

Although the slab in the video is only 8 to 12 inches (20 to 25cm) thick, if it propagates like this one did, 150 feet wide; it could be a problem in a gulley, over cliffs or into trees. The slabs reported from the Bitterroots and the Missions were larger and could have easily buried someone.
We received reports of similar activity from Wisherd Ridge near Missoula, from two popular backcountry areas in the Bitterroots and the Southern Missions. All these slabs were on East, Northeast and North slopes. All reported slabs were near ridgetops which have accumulated wind deposited snow.
So this tells me, even without a major storm or big weather change, a few inches here, a few inches there, add some wind loading, put this on the surface hoar from late January, and the recipe produces slab avalanches.
We also received numerous reports of whumphing and shooting cracks in the snow from the Rattlesnakes, the Southern Missions and the Bitterroots on Saturday. Tim and I noted whumphing and cracking on out tour Sunday also.
I have posted photos of slides in the Bitterroots, Missions and Rattlesnakes on our Photo Gallery www.missoulaavalanche.org/gallery.php?albumid=5416369076257222705 .
There are some pictures of slides near Gash Point in the Bitterroots at picasaweb.google.com/MontanaMountaineers/GashSlides20100213?authkey=Gv1sRgCND5zNn-k5WQWg# .

Weather Forecast and Avalanche Outlook
A shortwave system should pass through until midday today. Light snow accumulations are possible. Another system will approach the region on Tuesday morning. Snow amounts are predicted to be light. My radar is up pretty high right now as far as steep slopes are concerned. Any new amount of snow on top of this existing surface hoar layer will increase the sensitivity. For the time being, steep slopes on all aspects above 6000 feet are suspect .

Avalanche Hazard Ratings

The next advisory will be posted on February 19, 2010.
THANKS to all who sent in reports or photos this weekend!

Missoulaavlanche.org is currently running a survey this season to improve avalanche advisories and education. To access the survey visit www.surveymonkey.com/s/PC6Z5BH . Please take a few minutes to help us out. At the end you can enter a drawing to win a BCA Tracker Beacon, a Voile Avalanche Shovel or a missoulaavalanche.org t-shirt

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766 (530-9SNO).

February 12, 2010 Avalanche Advisory

Fri, 12 Feb 2010 00:00:00 MST

Good morning backcountry travelers! This is Steve Karkanen with backcountry avalanche information for Friday, February 12, 2010 from the West Central Montana Avalanche Center.

Thanks to Bob Skiles of Seeley Lake for the excellent snowmobile safety class he provided Avalanche Center and other Forest Service employees this past week. Bob's dedication to snowmobile and winter backcountry travel safety is commendable as he volunteers his time to teach snowmobile safety classes to many people in the community especially youth in the local school district.

Current Avalanche Danger

On all slopes steeper than 35 degrees and on all aspects above 6000 feet, the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. On all other terrain above and below 6000 feet, the avalanche danger is LOW, natural and human triggered avalanches are unlikely.

Weather and Snowpack Analysis

Once again, SNOTEL sites recorded minimal amounts of precipitation, if any at all. Mountain temperatures have cooled this week mostly due to the sun not breaking through the stratus clouds hovering at mountaintop locations most of the week.

The cooler temperatures are allowing faceted crystals to persist in the upper 20cm of snow as well as a thin layer of buried surface hoar about 18 inches deep in the snowpack.

We received an excellent but unconfirmed report from skiers in the southern Mission Mountains who triggered an avalanche last Saturday on a 40-degree ENE aspect at 8400 feet. They dropped a cornice and performed a ski cut with no results. One skier dropped in and the slope released while being skied. They estimated the slope propagated about 300 feet across and ran 1200 vertical feet. They reported this as a size class 2 to 2.5 and the bed surface was the buried surface hoar 16"-18" deep.

We were unable to confirm this but it is significant in that this avalanche shows the variability in stability across the region.

The group had radios, communicated the fracture to the skier who immediately cut left into a safe zone and safely watched the slide go by.

This is an excellent example of using safe skiing protocols, having outstanding communication equipment and skills as well as recognizing the potential hazard even after slope tests showed stable conditions. If the entire party chose to ski the slope together, this could have been a tragic situation. We are seeing many examples of poor route finding and poor safe skiing technique and happily, this group has shown how important good communication and decision-making is during periods when conditions cannot be trusted.

Yes, we are rating the hazard at Moderate and Low these days, but remember what we have been saying all along this winter. We have buried facets at the ground and at a couple of weak layers in the upper snowpack. Yes, it takes a lot of force to produce failure at these layers but when they fail, they fail with energy and will be very difficult to escape if you are caught in a slab avalanche under these conditions.

In the Rattlesnake, a layer of facets that formed between two ice crusts on slopes that were exposed to the sun last weekend are the weak link and have the most potential to fail if we receive significant snowfall. Weather conditions have been similar throughout the advisory area so I would expect to find similar upper snowpack conditions on any southerly slope above 6000 feet. This weakness frequently begins to develop during the type of weather conditions we have been watching the past 3 weeks. We measured steep temperature gradients in the upper 20cm of the snowpack (between the 2 crusts) which allowed the faceting process to continue and cooler temperatures this week are allowing this condition to persist. This is limited to slopes that are most prone to warming during the clear warm days (south to southwest) the past 2-3 weeks. A YouTube video we shot yesterday clearly shows this feature.

http://www.youtube.com/watch?v=Jn1gEmJzqFQ

We still find a buried surface hoar layer at mid-pack and depth hoar at the bottom 20cm but these layers are showing a lot of strength in all our observation site test pits, and it takes a lot of force to get these layers to fail.

Nevertheless, faceted snow cannot be trusted and the variability from one slope to another has to be factored into your decision-making.

Weather Forecast and Avalanche Outlook

Two weather systems will move through the Northern Rockies early Friday through midday Saturday. Each system will weaken dramatically as they move through a longwave upper ridge thereby limiting snowfall accumulation.

Without much new snow in the forecast, the avalanche danger will remain constant except for areas that see a lot of wind moving snow around. Cooler weather will allow the weaker layers to persist and high winds will quickly load leeward terrain even with the minimal amount of snow we received the past 4 days. Our overall snowpack is in a mostly safe condition but there are enough weak layers and so much variability that you have to assume dangerous conditions exist on some terrain features at the higher elevations. The avalanche reported to us from the Missions is all the evidence you need to know that it is possible to trigger an avalanche in some areas.

Please take the time to fill out our survey. This is your opportunity to let us know what you think the strengths and weaknesses of our program are and where we need to go in the future. Your comments do make a difference.

User Survey- Win an avalanche Transceiver, shovel or tee shirt

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO. Dudley will post the next observation on Presidents Day, Monday, February 15th.

February 8, 2010 Avalanche Advisory

Mon, 08 Feb 2010 00:00:00 MST

Posted 0600 on February 8, 2010.

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Monday, February 8, 2010.

Current Avalanche Danger

On all slopes steeper than 35 degrees and on all aspects above 6000 feet, the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. On all other terrain above and below 6000 feet, the avalanche danger is LOW, natural and human triggered avalanches are unlikely.

During periods of rapid warming the avalanche danger can quickly raise to CONSIDERABLE, natural avalanches are possible and human triggered avalanches likely. Many wet snow point release avalanches occur during periods when the sun bakes a slope for a few minutes. While these smaller avalanches by themselves do not present much of a hazard, it is possible the rapid load to a weak snow structure can result in these slides stepping down to the weak facets at the ground.

Weather and Snowpack Analysis

Since Friday, all the SNOTEL sites recorded minimal amounts of precipitation. Afternoon temperatures have been in the 30's each day and the wind has not been a factor this week. Shaded aspects are still skiing well and riding conditions are very good where the snow is deep enough.

Weak faceted crystals are present in the upper 20cm of the snowpack that fail during stability testing but this currently is not much of an avalanche problem. A heavy load of new snow will be of concern unless we see a couple of melt-freeze cycles that affect this layer. Afternoon temperatures have been above freezing at most mountain locations and this trend is expected to remain with us for a few more days.

Weather Forecast and Avalanche Outlook

Two comments sum up our conditions concisely. The first is from a weather forecaster who said; "High pressure will dominate through Thursday, what else would you expect in this El Nino winter?"

The other comment is from Dudley referring to a sun crust, which is the weakest feature in the current snowpack with 5-10cm of near-surface facets under the crust. He states; "the crust breaks with lots of energy but is just not very deep and does not constitute a hazard except for the breakable crust itself".

So now, we wait for the next big change in weather.

Everything we see in the backcountry right now is telling us we have a mostly stable condition but that does not give us the green light to abandon safe travel preparations and procedures.

We are seeing many examples of unsafe route finding in the Rattlesnake recently. We think most people are choosing these routes because of the low hazard right now but remember, people tend to follow the path of least resistance when skinning. Under these conditions that is proving to be across steep open slopes, over slope convexities and through areas where people are exposed for a longer period than necessary in places where we have seen avalanches triggered over the years. Yeah, you can get away with it under low hazard conditions but please understand that a skin track set through a starting zone or an area exposed to avalanche terrain will be followed by less knowledgeable individuals during high hazard conditions.

We live and die by our habits. Stick with proven safe travel protocol and avoid taking shortcuts through hazardous terrain. It's one thing to expose yourself to avalanche terrain for a couple of minutes when skiing, quite another to expose yourself, your partners and those who follow your track for 20 minutes or so while you trudge back up the hill for another run.

It is still possible to trigger an avalanche on some terrain features. Many places are still holding weak faceted snow especially on shallow rocky slopes. Pay particular attention to wind loaded terrain even after minor snowfall amounts. Always carry and know how to use a transceiver, probe and shovel and always travel with only one person exposed to hazardous terrain.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

February 5, 2010 Avalanche Advisory

Fri, 05 Feb 2010 00:00:00 MST

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Friday, February 5, 2010.

Thanks to Carole Johnson, a Lolo National Forest employee and Dan Frigard, an Idaho Panhandle National Forest employee, for their many weekly trips into the Saint Regis Basin and nearby areas to gather snowpack information for the avalanche advisory programs on the Lolo and Idaho Panhandle National Forests.

Current Avalanche Danger

On all slopes steeper than 35 degrees and on all aspects above 5000 feet, the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. Below 5000 feet, the avalanche danger is LOW, natural and human triggered avalanches are unlikely.

With our current conditions, just a few minutes of direct sun on steep southeast to southwest slopes can warm the snow rapidly enough to weaken the surface snow. During periods of rapid warming or during a rain event, the avalanche danger can quickly rise to CONSIDERABLE, natural avalanches are possible and human triggered avalanches likely.

Weather and Snowpack Analysis

Nearly all the SNOTEL sites recorded .20 to .40 inches of snow water equivalent or 2-4 inches of new snow since our report on Monday. Afternoon temperatures have been in the 30's each day and the wind has been mostly tame and not moving snow from one aspect to another. Shaded aspects are skiing well and riding conditions are very good where ever the snow is deep enough.

Snow pit profiles from one end of the Bitterroot to the other and in the Rattlesnake are showing a mostly stable condition with two buried surface hoar layers and the depth hoar we have been talking about all winter in some areas being the layers of concern.

Stability testing is showing that all these weak layers have gained strength. A layer of facets under a crust in the upper 20cm of the snowpack is the weakest feature and will need careful assessment during the next storm.

Yesterday the sun came out for a few brief moments and quickly began affecting the snow surface. Periods of warming especially with direct sun on steep southerly facing slopes can rapidly raise the avalanche danger.

Weather Forecast and Avalanche Outlook

A weak warm front will push through the area Friday with light snowfall confined mostly to the higher elevations. A weak disturbance over the weekend will keep light snow showers possible Saturday and Sunday. Expect 2 to 6 inches of snowfall in the 6000-8000 foot elevation range between today and Sunday.

Everything we see in the backcountry right now is telling us we have a mostly stable condition but that does not give us the green light to abandon safe travel preparations and procedures. It is still possible to trigger an avalanche on some terrain features. Many places are still holding weak faceted snow especially on shallow rocky slopes. Pay particular attention to wind loaded terrain even after minor snowfall amounts. Always carry and know how to use a transceiver, probe and shovel and always travel with only one person exposed to hazardous terrain.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

February 1, 2010 Avalanche Advisory

Mon, 01 Feb 2010 00:00:00 MST

Good morning, this is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for February 1, 2010.

Current Avalanche Danger
On slopes steeper than 35 degrees and on all aspects at elevations above 5000 feet, the avalanche danger is MODERATE. Natural avalanches are unlikely, human-triggered avalanches are possible.
In the Rattlesnake Mountains at elevations above 6000 feet on slopes steeper than 35 degrees the avalanche danger is MODERATE with pockets of CONSIDERABLE. On steep slopes with North and West Aspects in the Rattlesnakes human-triggered avalanches are probable.
On other terrain within the advisory area the avalanche danger is LOW.

Weather and Snowpack Analysis
The MODERATE hazard rating indicates there is the possibility of a slide on certain terrain features. Any steep areas where the snow is shallow from wind disbursement are suspect. The Rattlesnake Mountains received up to 6 inches of snow with over a half an inch of snow water. This heavy snow is sitting on top of surface hoar formed from Wednesday and Thursday night. Suspect areas in the Rattlesnakes with CONSIDERABLE hazard include steep slopes with Northeast, North, Northwest and West aspects.

We did get the snow to fail yesterday but it took a lot of force. We had some moderate failures on the early January surface hoar and the depth hoar from early December. Our tests are not showing clean fast shears with lots of energy but they are failing at some point during the test. Surface hoar formed on Wednesday and Thursday last week and the area received 3 to 6 inches of snow yesterday and last night. Snotel sites indicate the Rattlesnake Mountains received up to 7 inches which has settled to 6 inches.

Friday was sunny and warm at elevation. The sun destroyed the surface hoar on South and East slopes and caused some surface movement in many places Friday afternoon; a reminder that the snow will move when subjected to rapid warming. We observed plenty of surface sluffing yesterday on steep slopes while skiing. This was the new snow on top of the aforementioned surface hoar from the end of last week. The new snow from Sunday and Sunday night is dense and snotel sites in the area indicate it is settling rapidly, but, take into consideration the possibility of a human-triggered slide before jumping into steep slopes above 5000 feet.
The following You Tube video was shot while the new snow was coming in, it will give you an idea of the layers that are present. We got 6 to 7 inches of dense snow in the Rattlesnakes after the video was shot. That new heavy snow is sitting on the surface hoar shown in the video.

http://www.youtube.com/watch?v=Cz-7-_lk20c

Weather Forecast and Avalanche Outlook
Light snow continues to be a possibility during the next several days over high terrain. The snow is predicted to remain light and accumulate slowly. This scenario bodes well for avalanche stability; however if the winds do pick up snow could produce loading on lee sides. Keep this in mind as well as the other possibilities of weakness mention in the Current Avalanche Danger.

The next advisory will be posted on 2/5/10.

Missoulaavalanche.org is currently running a survey until 2/15/10 to improve avalanche advisories and education. To access the survey visit www.surveymonkey.com/s/PC6Z5BH . Please take a few minutes to help us out. At the end you can enter a drawing to win a BCA Tracker Beacon, a Voile Avalanche Shovel or a missoulaavalanche.org t-shirt.

If the Beacon Park is not set up at Snow Bowl ski are you can get the control box from the summit patrol shack. The Snow Bowl Patrol will retrieve it when they sweep. For all Beacon Park information go to www.missoulaavalanche.org/beacon_training.php .

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766 (530-9SNO).

January 29, 2010 Avalanche Advisory

Fri, 29 Jan 2010 00:00:00 MST

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Friday, January 29, 2010.

Current Avalanche Danger

The avalanche danger is LOW at all elevations with the exception of recently wind-loaded terrain steeper than 35 degrees above 5000 feet where the avalanche danger is MODERATE.

Continued moderate temperatures and light snowfall continue to give our snowpack plenty of time to strengthen. Our high elevation snowpack is generally stable but isolated pockets of instability still exist. These areas of concern are recently wind-loaded slopes steeper than 35 degrees mostly at the higher elevations of the advisory area.

Weather and Snowpack Analysis

Most locations picked up another 2 to 4 inches of snow since Monday. High humidity the past 24-48 hours has helped surface hoar crystals form on top of everything making for some very enjoyable skiing.

Reports from the Bitterroot Mountains at Lost Trail Pass, Lolo Pass, Lookout Pass and the Rattlesnake Mountains all indicate continued strengthening of the weak layers described in earlier reports. We're close to the point of not even mentioning them anymore since it takes so much force to make them fail, but we have yet to be tested by a big storm.

Our primary concern, once it begins snowing again, will be this current crop of surface hoar crystals. These 5-10mm size crystals tend to be our biggest avalanche problem once buried. Sun, warm temperatures and wind easily and quickly destroy these crystals when they are exposed, but when buried, they create problems for us as they persist for weeks as a weak layer. In addition, we can never be sure of where they formed, and if they were destroyed, prior or during the big storm we all desire.

Weather Forecast and Avalanche Outlook

High pressure shifts eastward over western Montana and will persist through Friday. A Pacific weather system approaches the region Saturday, which will push a significant surge of moisture and energy across north central Idaho and western Montana late Saturday night and Sunday. The best moisture enhancement will be the Clearwater, Bitterroot and Mission mountains north to Glacier Park. Winds start out from the south and east but turn westerly and increase at higher elevations Saturday.

Please take the time to fill out our survey. This is your opportunity to let us know what you think the strengths and weaknesses of our program are and where we need to go in the future. Your comments make a difference. We wouldn't have an avalanche center here if it wasn't for your written comments a few years ago and we wouldn't be issuing advisories 2 days each week and as needed if it wasn't for your comments, participation and financial support of the West Central Montana Avalanche Foundation. THANKS FOR YOUR CONTINUED SUPPORT!

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

January 25, 2010 Avalanche Advisory

Mon, 25 Jan 2010 00:00:00 MST

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Monday, January 25, 2010.

Current Avalanche Danger

The avalanche danger is LOW at all elevations with the exception of recently wind-loaded terrain steeper than 35 degrees above 5000 feet where the avalanche danger is MODERATE.

Our high elevation snowpack is generally stable but isolated pockets of instability exist. These areas of concern are recently wind-loaded slopes steeper than 35 degrees mostly at the higher elevations of the advisory area.

Weather and Snowpack Analysis

Since Friday (1/22) our area has received 2 to 4 inches of snow at most SNOTEL sites but very high northeast to southeast winds. For a 24- hour period on Friday, recorded wind speeds were in the 30mph range with gusts into the 70's. This high wind scoured the secret stashes and laid some very fine crystalline powder onto normally ignored west facing slopes. Not a lot, but if you were paying attention, you found some very good skiing over the weekend. Wind can put down more new snow on the leeward aspects than most of the storms we have seen recently.

Reports from the southern Bitterroot at Lost Trail Pass, Lolo Pass and the Rattlesnake all indicate continued strengthening of the weak layers described in earlier reports. Two buried surface hoar layers are still prominent in the upper snowpack but it takes more force to produce failures. The depth hoar at the base of the snowpack is still obvious in most pit locations and does fail but it takes a lot of force to produce failures at this level.

The problem now is how much snow or weight will it take, to initiate an avalanche. I think it will take a lot until we start seeing heavy wet Pacific storms moving through the area. For the time being, there is not much new snow in the forecast. Hence, the low avalanche danger rating.

Weather Forecast and Avalanche Outlook

Sorry, but it does not look good for new snow. A weak shortwave disturbance with limited moisture moves through the northern Rockies Monday allowing snow showers to linger through Wednesday as another trough passes through West Central Montana. Models are predicting that another high-pressure system will move in by mid-week with warm temperatures at the higher elevations.

The good news in all of this is that we currently have more stable conditions than our neighbors just 200 or so air miles east and south of us. The Gallatin NF Avalanche Center in Southwest Montana just experienced one of the largest and prolonged avalanche cycles in many years and the Sawtooth NF Avalanche Center in Sun Valley ID is currently dealing with a very dangerous snowpack condition.

Our snowpack structure was very similar to what these areas are now dealing with. So why the difference? Our entire advisory area is at lower elevations therefore influenced by warmer air temperatures and inversions. Prolonged warm or moderate temperatures strengthen weaknesses within the snowpack.

During El Nino winters, a split Jet Stream takes the heavier moisture around us to the north and south therefore fewer snowstorms. We just came out of a 2-3 year La Nina cycle that favored western Montana with above normal snowpack and happy satisfied skiers and snowmobilers.

Keep in mind that we have a snowpack structure in many areas that cannot be completely trusted. We still have potential for large destructive avalanches under the right conditions, just not now and hopefully not at all.

Thanks to those of you who continue to send us excellent snowpack profiles and very thorough reports. It makes a difference in the quality of our advisories and Dudley and I appreciate the extra time it takes for you to send this information to us. THANKS!

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

January 22, 2010 Avalanche Advisory

Fri, 22 Jan 2010 00:00:00 MST

Good Morning! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Friday, January 22, 2010.

Current Avalanche Danger

On slopes steeper than 35 degrees and on all aspects at elevations above 5000 feet, the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible.

Below 5000 feet, the avalanche danger is LOW.

Weather and Snowpack Analysis

Temperatures have remained moderate since the MLK holiday and most sites received just a couple of inches of new snow. Enough to "freshen up" the snow on shaded slopes. On the more south facing aspects, a sun crust formed during the sunny afternoon Wednesday.

These moderate temperatures continue to help strengthen the overall snow stability condition and most areas are now mostly stable but we still have a couple of persistent features that are keeping us in the moderate rating.

Near Lost Trail Pass observers are reporting a layer of buried surface hoar has actually weakened as stability tests are producing failures 45cm deep with moderate force but with high quality shears with energy and propagation across the column in extended column testing. Temperatures have been cooler and the snowpack shallower in this area than in our northern locations.

All other locations including an area near Camas Peak in the central Bitterroots at 8600 feet, Tom Beal Park near Powell ID at 7900 feet, Lookout Pass and the Rattlesnake at 7600 feet are all showing similar snow structure but strengthening of the weaker layers with the moderate temperatures.

South aspects are shallow and are going to be touchy if we receive significant snowfall in the next few days. Sun crusts that formed 2 and 4 days ago are showing near-surface facet growth between two sun crusts, which easily fail during skiing, and testing. You can see an example of this on our photo page. Steep open south slopes will be weak once loaded. Moreover, the depth hoar we have been talking about all winter is still present on all aspects. Shallow pockets will be of more concern for deep failures at this layer.

Weather Forecast and Avalanche Outlook

Mild and dry conditions will transition to cool and snowy over high terrain during the next few days. A broad Pacific storm system will split in two over the Pacific Northwest early Saturday with snow developing and snow ratios increasing with time. Expect the main snow event to end during Sunday with high pressure bringing more dry and mild weather.

We currently have the most stable conditions of the winter this week. Check out this YouTube video of a Rutschblock in the Rattlesnake for an example of what we are seeing. The two weak layers described in earlier reports may become reactive if the area receives a heavy load of snow. The places to watch will be any open wind loaded slope steeper than 35 degrees. It is possible that higher elevations could see 12-16 inches of snow this weekend. That will certainly be enough to bring our snowpack back to life if it comes in all at once. If it spreads out over time, we should be in good shape stability wise.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

Martin Luther King Day 2010 Avalanche Advisory

Mon, 18 Jan 2010 00:00:00 MST

Good morning, this is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for Martin Luther King Day, 2010.

Current Avalanche Danger
On slopes steeper than 35 degrees and on all aspects at elevations above 5000 feet, the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. On other terrain within the advisory area the avalanche danger is LOW.

Weather and Snowpack Analysis
The MODERATE avalanche danger is related to a surface hoar layer that is buried about 40cm (16") from the surface. On some locations within the advisory area this layer is still reacting cleanly to stability tests. If you are recreating on steep slopes above 5000' it would be prudent to check for instabilities in the top couple of feet.

The area received a very modest amount of snow over the weekend. We had rain up to about 5500' in elevation and small amounts of dense snow above the rain level.

The depth hoar that formed in early December is still around on slopes that haven't already avalanched, but it is not reacting to stability tests.

Moderate temperatures at elevation (anywhere from the high 20's to the low 40's) are helping stabilize the snowpack.

Weather Forecast and Avalanche Outlook
The unsettled weather pattern is expected to continue this week. The Weather Service actually used the dreaded words "El Nino". We should see some precipitation each day, but amounts are expected to remain low. Snow levels should be approximately 3000 feet. One word of warning, if it does start to rain on the snow pack when you are recreating or working in the mountains; you should stay off steep slopes. The immediate effect of rain would destabilize the current conditions. Rapidly-added weight almost always means rapidly-rising avalanche danger.

Expect our avalanche conditions to remain the same until we see significant changes in the weather.

Steve Karkanen will post the next advisory on 1/22/10.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

For Beacon Park information go to www.missoulaavalanche.org/beacon_training.php.

January 15, 2010 Avalanche Advisory

Fri, 15 Jan 2010 00:00:00 MST

Good Morning! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Friday, January 15, 2010.

Current Avalanche Danger

On slopes steeper than 35 degrees and on all aspects at elevations above 5000 feet, the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible.

Below 5000 feet, the avalanche danger is LOW.

Weather and Snowpack Analysis

For the past five days afternoon temperatures at all SNOTEL sites reached into the upper 30's and many locations even saw a bit of sun for a few hours.

Our concern all winter has been the depth hoar or facets at the base of our snowpack that formed during the December deep freeze and later buried and sort of preserved/insulated from later moderate temperatures. The more recent concern is a surface hoar layer that formed over the holidays. Many avalanches ran during the last heavy precipitation event January 4-5 and most of these involved the upper layer of buried surface hoar.

The lack of new snow and moderate temperatures this past week have not done much to improve the skiing and riding conditions but it has sped up the settlement process which strengthens these weaknesses we've been describing.

All observers are talking about failures at the level of the buried surface hoar, about 10 to 15 inches deep, but it is taking a lot of force to get this layer to fail. Compression test scores at this level were in the moderate to hard failure range. Some test sites display the potential for this layer to propagate across a slope but much stronger than reported earlier. Other sites are showing a very strong condition.

A good example of this variability is the results observers at Lookout Pass and in the Rattlesnake were getting with the Rutschblock test.

Rattlesnake: RB score 6, Q1 failure at 35cm on the buried facets (depth hoar) above an old melt-freeze crust.

Lookout Pass: RB score 3, Q1 failure at 70cm on the buried surface hoar.

This surface hoar layer is widespread throughout the region but the Lookout Pass test area at 5800 feet has remained cooler than the higher elevation site in the Rattlesnake at 7200 feet. Cooler temperatures help prolong persistence of weak layers. In the case of the Rattlesnake test site, the warmer temperatures have settled the snowpack quicker than normal for this time of year so the surface hoar layer had a good opportunity to gain strength during the warm spell.

We believe the super weak facets at the ground (50cm at the end of December) have collapsed in many areas and are not as much of a stability factor as in our earlier observations. We see about 20cm of facets near the ground where we were seeing 50cm 3 weeks ago. A very good sign of strengthening but when a test area failed, it failed with a lot of energy to the ground and propagated across the slope. South aspects are more suspect than other aspects. We see easier failures at the level of both features on south aspects or any slope where the snow is shallow or rocky.

Take home message: Never trust a layer of faceted snow.

Weather Forecast and Avalanche Outlook

A weak ridge of high pressure will build over the area Friday. Moisture streaming into northwest Montana may cause showers Friday night into Saturday. A mid-level jet stream will develop over the area late Friday causing extremely strong westerly wind at higher elevations near the continental divide. Expect little precipitation for the next 48 hours with snow levels near 5000 feet.

Continued milder conditions will strengthen the overall snow structure but we are not completely free from seeing larger slabs bust out under the right amount of force.

We rely heavily on the many excellent observations people are sending us this winter. They help us produce a more accurate avalanche forecast since our resources are limited. Special thanks to everyone who sent us quick emails, left messages or talked to us in the backcountry during our travels to let us know what they were seeing during the period when conditions were sketchy over the holidays. Your information may save a life some day.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

Missoulaavlanche.org is currently running a survey to improve avalanche advisories and education. Please take a few minutes to fill out the survey. At the end of the survey you can enter a drawing to win a BCA Tracker Beacon, a Voile Avalanche Shovel or a missoulaavalanche.org t-shirt.

January 11, 2010 Avalanche Advisory

Mon, 11 Jan 2010 00:00:00 MST
Posted 0700 on January 11, 2010.

Good Morning! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Monday, January 11, 2010.

Current Avalanche Danger

Avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. Sun exposed slopes may warm enough today to see wet slides begin to occur. The avalanche danger will quickly rise to CONSIDERABLE when snow begins melting on these slopes.

Below 5000 feet, the avalanche danger is LOW.

Weather and Snowpack Analysis

Stability testing in the Rattlesnake and in the Bitterroot Mountains near Hoodoo Pass is showing a strengthened condition of both the buried surface hoar and the deep faceted snow near the ground.

The weakest slopes are those that are shallow where it is easy to punch through to the rotten snow at the ground especially near rocks and trees.

Ambient air temperatures Sunday reached into the mid to high 30's so roller balls and a few wet point release avalanches moved on the sun exposed areas. The best skiing was in the shade but these colder slopes are also holding instabilities longer. The buried surface hoar layers that are about a foot to a foot and a half deep were failing but with more force required than a few days ago. Many people were out safely skiing steeper lines Sunday than we have seen all winter.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting that warm and dry conditions will be present over high terrain through Monday afternoon. By Monday evening, a moist southwesterly flow and a weak embedded Pacific storm system will increase chances for precipitation. Expect snowfall amounts to be light.

The warmer temperatures will initially weaken our snow surface and I would expect to see wet avalanche activity on steep sunny slopes today. When the snow warms to this point, it is not a good time to be on or under anything steep. Remember, we still have faceted layers that cannot be trusted whenever conditions are changing. A small wet surface slide could easily step down to the weaker layers and cause a large avalanche.

These milder conditions will help to strengthen the overall snow structure but we are not completely free from seeing larger slabs bust out under the right amount of force.

We rely heavily on the many excellent observations people are sending us this winter. They help us produce a more accurate avalanche forecast since our resources are limited.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

January 8 Avalanche Advisory

Fri, 08 Jan 2010 00:00:00 MST
Posted 0630 on January 8, 2010.

Good Morning! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Friday, January 8, 2010.

Current Avalanche Danger

We have downgraded the Avalanche Danger issued Wednesday from HIGH to MODERATE. There are isolated areas where the avalanche danger is CONSIDERABLE. This rating is for all elevations and aspects above 5000 feet on slopes steeper than 35 degrees. This higher avalanche danger exists on steep open terrain where it is possible to trigger an avalanche from rock outcrops or shallow places where the weight of a sled or skier can cause failure that propagates across a larger area.

Below 5000 feet, the avalanche danger is LOW.

Weather and Snowpack Analysis

We have two major concerns with the current situation.

Surface hoar developed during a period of cold clear weather over a week ago, that is now buried across widespread mountain locations. Many small avalanches were reported during and after the storm cycle that passed through western Montana Monday and Tuesday when high moisture content snow overloaded this weak layer. This layer is showing signs of gaining strength but was still failing with a moderate amount of force and with fast clean fracture propagations during stability tests Thursday.

The second concern is the layer of facets at the ground that are continuing to fail in stability tests as we have shown in our YouTube videos. All locations are reporting that it is getting harder to initiate failure at this level but again, when it fails, it fails with energy, cleanly and wants to propagate across the slope. These two layers are widespread throughout Western Montana on all aspects above 6000 feet in areas North of Missoula and above 5000 feet in the Lolo and Lookout Pass areas. The buried surface hoar is spotty but all our observers found it Thursday. Slopes that avalanche on the surface hoar layer may easily entrain enough snow and weight to initiate failure of the faceted snow near the ground. These may be large destructive avalanches similar to what we experienced last year at this time.

Please review our recent YouTube videos here:

Missoula Avalanche YouTube Videos

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting a ridge of high pressure to remain anchored over the northern Rockies until a Pacific weather system pushes into the area late Friday. The upper airflow will come from the southwest bringing mild temperatures and light snowfall. Weather models depict the ridge of high pressure to rebuild with dry mild conditions.

The anticipated mild weather conditions will allow our snowpack to gain strength. It is going to take several weeks for the weakness at the base of the upper elevation snowpack to gain strength. The big problem with making go, no-go decisions in avalanche terrain these days is the incredible variation in results we see in our stability tests. The bottom line is that we have a significant layer of rotten, faceted snow at the ground that cannot be trusted and now another weak layer in the upper snowpack that caused several avalanches earlier this week.

We noted surface hoar was developing again with the cold clear weather so keep track of where this feature is located and what happens to it as the weather changes.

We rely heavily on the many excellent observations people are sending us this winter. They help us produce a more accurate avalanche forecast since our resources are limited.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

AVALANCHE WARNING for January 6, 2010

Wed, 06 Jan 2010 00:00:00 MST
AVALANCHE WARNING JANUARY 6, 2010

An Avalanche Warning is in effect for the mountains of West Central Montana. Heavy wet snowfall is accumulating on a very weak snowpack structure throughout our advisory area. This warning includes all aspects and elevations above 6000 feet in the Bitterroot, Rattlesnake and the Southern Swan and Mission Mountains near Seeley Lake.

Current Avalanche Danger

Above 6000 feet on all aspects, the avalanche danger is HIGH. All SNOTEL sites are reporting high Snow Water Equivalent (SWE) with the northern locations receiving the most precipitation. Stuart Peak and North Fork Jocko SNOTEL sites report close to 1.5 inches of SWE and most Bitterroot Range SNOTEL sites report .80 inches of SWE in less than 24 hours.

We have two major concerns with the current situation.

In areas that earlier reported surface hoar development last week, this new snow will easily overload that weak layer. On Monday, we received reports of small avalanches failing on this buried surface hoar layer in the Bitterroot Mountains near Lolo Pass and near Lost Horse west of Darby. The backcountry area near Lost Trail Ski Area also has a significant buried surface hoar layer.

The second concern is of course the layer of rotten nasty facets at the ground that are continuing to fail in stability tests as we have shown in our YouTube videos. This layer is widespread throughout Western Montana on all aspects above 6000 feet. The surface hoar is spotty. Slopes that avalanche on the surface hoar layer may easily entrain enough snow and weight to initiate failure of the faceted snow near the ground. These may be large destructive avalanches similar to what we experienced last year at this time.

Below 6000 feet, the avalanche danger is highly dependant on the amount of snow accumulating. Many of these areas had rain yesterday and are now refreezing so the avalanche danger is mostly LOW. Most of the recent snow accumulation is above 6000 feet.

Weather and Snowpack Analysis

We will be out Wednesday in the Rattlesnake and will have observers in all our normal locations Thursday so we will give a more thorough report Friday morning. I expect this avalanche warning will be short-lived as we are expecting the moisture to end within the next few hours and temperatures to drop quickly. Please review our recent YouTube videos here:

Recent snow stability testing.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting the current precipitation event to end with a much cooler air mass to reside over the area with clearing skies and a ridge of high pressure approaching from the west. Expect temperatures to drop to near zero Wednesday night.

Avalanche conditions will strengthen as temperatures cool. It is going to take several weeks for the weakness at the base of the upper elevation snowpack to gain strength. I mentioned in an earlier advisory that if our area received an inch or more of SWE, I would expect to see widespread avalanche activity on all aspects especially in areas where the surface hoar was buried.

We rely heavily on the many excellent observations people are sending us this winter. They help us produce a more accurate avalanche forecast since our resources are limited.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

January 5 Avalanche Advisory Update

Tue, 05 Jan 2010 00:00:00 MST
Good afternoon this Dudley Improta with an avalanche hazard update for January 5, 2010. On all slopes above 6000' and steeper than 30 degrees there is CONSIDERABLE avalanche danger.
Many areas in West Central Montana have received over an inch of snow water equivalent (wet heavy snow). This snow fell on a weak layer in the top 10 inches of the snow pack. There is also a weak layer at the bottom of the pack. This wet dense snow may easily overload these existing weak layers. There is increased danger if there is rain on the snow pack.
My advisory from Monday Jan. 4 is below and explains these layers in the snow.

From January 4:

Weather and Snowpack Analysis
I don't want to sound like a broken record (cd or mp3) but we have an interesting scenario in West Central Montana right now. The region received anywhere from 5 to 10 inches of new snow since New Year's Day. Before the new snow arrived surface hoar had formed on the top of the snowpack. The surface hoar had been destroyed by sun and wind in the Rattlesnakes but not in the Bitterroots. The avalanche near Lolo Pass reported in the "current danger" was the new snow running on the surface hoar. We had the same surface failures in stability tests in the Rattlesnakes but it appeared to be a density change in the snow (the snow came in cold and finished warm). What is worrisome is in stability tests the snow is still failing on the depth hoar formed from early season.
The top layer avalanching could be a problem if it went into a terrain trap (i.e. over a cliff or into a gulley) and the top layer avalanching could step down to the weak snow in the bottom of the pack. There is some skiing or riding to be had out there but you need to pay close attention to steep terrain.
The You Tube shot explains the variability in our pit tests. But the difference in the tests has been the amount of force applied; the same layer continues to collapse cleanly.
I noted the same variability with backcountry recreationists this weekend. I talked to some cagey veteran backcountry skiers who turned around after snow observations. I saw some folks ski a conservative, anchored line one at a time and I saw some riders hucking cliffs with their buddies standing immediately below. The activity from the last observation is not advisable.

http://www.youtube.com/watch?v=PtgzUmxshgM

Weather Forecast and Avalanche Outlook
Pacific Moisture may collide with cold Canadian air over the region on Monday and Tuesday. As of this advisory it's not clear how quickly the Canadian air will surge into Western Montana. Moderate to heavy snowfall is predicted along the Continental Divide along with Northeast winds. Wednesday should bring drier and colder conditions.
Expect the surface instability to increase with new snow amounts. With more snow the surface slab will be thicker as well. If we get new snow, winds and the predicted colder air the avalanche hazard will not decrease.
Keep in mind that our winds generally come out of the Southwest. Northeast winds are predicted for this storm; which makes all steep slopes above 6000' suspect.

Steve Karkanen will post the next advisory on 1/8/10.

January 4 Avalanche Advisory

Mon, 04 Jan 2010 00:00:00 MST
Good morning, this is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for January 4, 2010.

Current Avalanche Danger
There are pockets of CONSIDERABLE avalanche danger above 6000' on terrain steeper than 35 degrees.
We are seeing failures in our stability tests in the top 25cm (10") of snow and in the depth hoar toward the bottom of the snowpack. We received a well-documented report of a skier-triggered slab near Lolo Pass on 1/2/10. This avalanche was on a steep slope and was 25cm (10") deep from the surface. We have also received reports of other skier and rider - triggered avalanches in the Bitterroot near Lolo Pass and Lost Horse Creek.
These pockets of CONSIDERABLE danger are on steep slopes void of anchors or rollovers associated with rocky outcroppings.
On other terrain above 6000' and steep terrain void of anchors above 5000' the avalanche danger is MODERATE.
On all remaining terrain above and below 5000' the avalanche danger is LOW.

Weather and Snowpack Analysis
I don't want to sound like a broken record (cd or mp3) but we have an interesting scenario in West Central Montana right now. The region received anywhere from 5 to 10 inches of new snow since New Year's Day. Before the new snow arrived surface hoar had formed on the top of the snowpack. The surface hoar had been destroyed by sun and wind in the Rattlesnakes but not in the Bitterroots. The avalanche near Lolo Pass reported in the "current danger" was the new snow running on the surface hoar. We had the same surface failures in stability tests in the Rattlesnakes but it appeared to be a density change in the snow (the snow came in cold and finished warm). What is worrisome is in stability tests the snow is still failing on the depth hoar formed from early season.
The top layer avalanching could be a problem if it went into a terrain trap (i.e. over a cliff or into a gulley) and the top layer avalanching could step down to the weak snow in the bottom of the pack. There is some skiing or riding to be had out there but you need to pay close attention to steep terrain.
The You Tube shot explains the variability in our pit tests. But the difference in the tests has been the amount of force applied; the same layer continues to collapse cleanly.
I noted the same variability with backcountry recreationists this weekend. I talked to some cagey veteran backcountry skiers who turned around after snow observations. I saw some folks ski a conservative, anchored line one at a time and I saw some riders hucking cliffs with their buddies standing immediately below. The activity from the last observation is not advisable.

http://www.youtube.com/watch?v=PtgzUmxshgM

Weather Forecast and Avalanche Outlook
Pacific Moisture may collide with cold Canadian air over the region on Monday and Tuesday. As of this advisory it's not clear how quickly the Canadian air will surge into Western Montana. Moderate to heavy snowfall is predicted along the Continental Divide along with Northeast winds. Wednesday should bring drier and colder conditions.
Expect the surface instability to increase with new snow amounts. With more snow the surface slab will be thicker as well. If we get new snow, winds and the predicted colder air the avalanche hazard will not decrease.
Keep in mind that our winds generally come out of the Southwest. Northeast winds are predicted for this storm; which makes all steep slopes above 6000' suspect.

Steve Karkanen will post the next advisory on 1/8/10.

For Beacon Park information go to http://www.missoulaavalanche.org/beacon_training.php .

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766 (530-9SNO) .

New Years Day 2010 Avalanche Advisory

Fri, 01 Jan 2010 00:00:00 MST
Happy New Year! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for the 2010 New Year.

Current Avalanche Danger

Above 6000 feet on all aspects, the avalanche danger is MODERATE with pockets of CONSIDERABLE avalanche danger on some terrain features where snow has covered anchors. Treat wind loaded leeward ridgelines and some cross-loaded terrain with rock outcrops and open bear grass slopes with caution.

Below 6000 feet, the avalanche danger is LOW.

Weather and Snowpack Analysis

SNOTEL locations have received only a few inches of snow the past 72 hours with temperatures in high teens and 20's. We see a definite strengthening of our snowpack over time but we are very concerned about how much new weight it will be able to handle. All reporting locations are reporting much stronger stability test scores but when a failure occurs, they are deep, fast and clean at the level of the facets that formed during the cold weather in December.

Many locations in the Bitterroot are reporting a layer of surface hoar that formed earlier this week is buried 2 to 8 inches deep and is failing easily during stability testing. We did not see this surface hoar layer during our tour in the Rattlesnake.

Nearly all stability tests are indicating moderate stability but there are pockets where we see easy failures particularly on south aspects, in rocky areas and where the snow is still very shallow. We are not seeing the widespread collapse noise and fracture propagations we reported 2 weeks ago.

A fair amount of time has passed and our snowpack has slowly been gaining strength. Stability test scores are showing this but the problem is when the test area fails; it still fails with a lot of energy, is fast, clean and easily propagates.

This YouTube video is of a Rutschblock (score is 5) on a northeast aspect and shows a fast clean shear at the interface of the slab and the faceted snow that formed in early December.

http://www.youtube.com/watch?v=uk88abVz5n0

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting that a warm Pacific storm system will be moving through the area Friday morning. Moisture and energy with a northwest flow will move in behind this system with a chance of accumulating snow across the central and northern Clearwater Mountains and Bitterroot Range through the weekend. Warm air Friday will reduce snow ratios so look for this snow to be heavy and wet. Cold air aloft will move in Saturday increasing snow ratios.

Avalanche conditions will slowly strengthen as we continue to receive small amounts of snow. It is going to take several weeks for the weakness at the base of the upper elevation snowpack to gain strength and these short bursts of snow are not enough to affect the weak layer deep within the pack. If our area receives significant snow of an inch or more of snow water equivalent (SWE), I would expect to see widespread avalanche activity on all aspects. Areas where the surface hoar was buried will be sensitive with any amount of new snow and wind loaded terrain will be very sensitive.

The next updated avalanche advisory is January 4, 2010.

We rely heavily on the many excellent observations people are sending us this winter. They help us produce a more accurate avalanche forecast since our resources are limited.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

December 28 Avalanche Advisory

Mon, 28 Dec 2009 00:00:00 MST
Good morning, this is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for December 28, 2009.

Current Avalanche Danger
There are pockets of CONSIDERABLE avalanche danger above 7000' on terrain steeper than 35 degrees. Terrain with talus slopes, boulder fields and rock outcroppings are holding the loose snow towards the bottom of the snowpack.
Overall the snow has settled since last week; but we are still seeing weak failures with stability tests around the aforementioned rocky features. The wind has been moving snow onto North, Northeast and East aspects as well. Any wind loading on the rocky areas described will increase the chance for an avalanche.
On other steep slopes above 7000' and slopes above 6000' that are steeper than 35 degrees and void of anchors the avalanche danger is MODERATE.
On all remaining terrain above and below 6000' the avalanche danger is LOW.
We are, once again, describing a situation that varies with elevation, aspect, steepness and the underlying character of the slope. We have a low snowpack and the temperatures have been wildly variable at elevation. On shaded slopes, where it has stayed cold, the temperatures have worked on the snowpack and the weak, loose snow Steve Karkanen has described for the last two weeks remains near the bottom.

Weather and Snowpack Analysis
We have had no appreciable snow since Christmas Day. As I mentioned, the temperatures in the mountains have been variable to say the least. Anyone who has been recreating at elevation has experienced the warm sunny temperatures on Southerly and Westerly slopes and the bitter cold temperatures on Northerly and Easterly slopes. Winds have been moderate at elevation; but strong enough to move snow on the high ridges. There are wind loaded slopes and cornice buildup on ridges above 7000'.
Crystal clear skies above 6000' have allowed all this warming and cooling. The cold faceted snow at the bottom of the pack remains on shaded protected slopes, particularly around rocky areas. Spaces between the rocks allow the air to move through the snow to create and hold the loose weak crystals. On our tour Christmas Eve we noted all the slopes that had avalanched had Northerly aspects and rock outcrops with steep rollovers.
Saturday we had some pleasant low angle turns through surface hoar. The cold clear nights have created an abundance of surface hoar. The sun on the clear days has destroyed these crystals on Southerly and Westerly slopes. The surface hoar is beautiful now but may create a weak layer on those shaded protected slopes when it snows again (note my optimism).
For the time being, carefully analyze the terrain aspect, elevation and character (rocky features) before committing to any steep slopes

Weather Forecast and Avalanche Outlook
The ridge of high pressure we are experiencing is supposed to break down today as a pacific system moves in. Possibly we will see light snow in the mountains tonight and then better chances for snow by Tuesday. There is snow in the forecast for the week due to Southwest flows.
I would expect the avalanche danger to decease slightly until we experience a significant weather change or snowfall. There is a possibility of significant snow in the mountains by Wednesday. I would remain cautious around the steep, rocky terrain I described in this advisory.

The next avalanche advisory will be posted on New Year's Day.

If you haven't visited the Missoula Weather Service's Snow/Avalanche page at www.wrh.noaa.gov/mso/avalanche/ , I advise you to do so. Although the snow forecast is a bit depressing right now, the newly designed page has some great information.

For Beacon Park information click on the link on our home page.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766 (530-9SNO).

Christmas Day Avalanche Advisory

Fri, 25 Dec 2009 00:00:00 MST
Merry Christmas! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Christmas, 2009.

We have been experiencing technical problems with our server this morning so we are posting later than usual. Sorry about the delay.

Current Avalanche Danger

The avalanche danger above 7000' on terrain steeper than 35 degrees where snow has covered anchors has improved but not enough to let your guard down. CONSIDERABLE avalanche danger exists in these locations.

Moderate temperatures helped settle the snowpack in many locations and on some specific aspects helped strengthen the weak interface between the newest snow and the weak sugary base of facets we have been concerned about.

At lower elevations, 5000 to 7000 feet, and in areas where the snow has not yet buried anchors the avalanche danger is MODERATE.

Below 5000 feet, the avalanche danger is LOW.

Weather and Snowpack Analysis

Very little snow accumulated since our last report Monday but what we did get was enough to tip the balance on many slopes. We received reports that east to north aspects avalanched on their own and we saw evidence of this on a tour in the Rattlesnake Thursday. These avalanches probably ran during the warm wet weather Sunday and Monday.

Mountain temperatures again plummeted Wednesday night and Thursday but are expected to return to a more normal pattern by the weekend. These cool temperatures will allow the facets we have been talking about to persist and lose some of the strength built up during the warm spell.

The next problem developing with this current weather condition is surface hoar.

Everybody is seeing it, it is not a problem now but if it is buried before it is destroyed by the wind or sun, we will be describing another weak layer backcountry travelers need to consider before crossing or jumping onto slopes steeper than 30 degrees.

We were experiencing moderate range stability test scores in the Rattlesnake as well as in the Bitterroots from Lost Trail to Lookout Pass.

A fair amount of time has passed and our snowpack has slowly been gaining strength. Stability test scores are showing this but the problem is when the test area fails; it fails with a lot of energy, is fast, clean and easily propagates.

Compression test scores throughout the area were failing in the high teens and 20's for a moderate stability result but all with high quality, quick and smooth planar shears. On a west to southwest aspect at 7800' an extended column test failed on isolation (ECTPV) and compression test scores were consistent CT5 all with high quality shears. A southeast aspect with similar depth appeared to be the most stable slope with CT scores at 23. As we moved to more east facing slopes the snow was weaker with CT scores of 19, ECTP19 and a Rutschblock score of 4; failed on one hard jump.

All these failures are at the interface of the slab and the faceted snow near the ground that formed in early December.

Many high elevation sites look very tempting right now and the next big snow will be just too good to pass up on an opportunity too get those first tracks in. There is an incredible amount of variability in our snowpack right now as we saw yesterday. The one thing you can count on is that above 7000 feet, there is now a slab sitting on about 50cm of super weak faceted snow. Yes, it is gaining strength, but slowly, and maybe only enough strength for one person to get away with it.

This YouTube video shows why we are concerned about the future of our snowpack in the higher, steeper ground in the Bitterroots, Swan and Mission Mountain ranges.

www.youtube.com/watch?v=d2uS709pCG4

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting that our ridge pattern will shift inland this weekend with drier air moving into the area. We can expect to see strong surface inversions for the next few days. The next good opportunity for moisture appears to arrive by mid-week when the high-pressure ridge breaks down Tuesday under an approaching Pacific weather system.

Expect avalanche conditions to continue to slowly strengthen but quickly deteriorate if we receive heavy new snowfall. It is going to take several weeks for the weakness at the base of the upper elevation snowpack to gain strength.

The next avalanche advisory will be posted on December 28.

Transceiver Park Information

There are now 3 Beacon Basin avalanche transceiver parks in operation in western Montana. They are located at Lost Trail Powder Mountain, Lolo Pass Visitor Center and Montana Snowbowl. All three will be available for use for the entire season during operating hours at the ski areas and Lolo Pass Visitor Center.

The Beacon Basin at Montana Snowbowl requires purchase of a lift ticket to access the site located at the backcountry access point to Point Six and is available everyday. If the unit is not there, check in with the ski patrol in the Warming Hut at the top of the Lavelle lift and they will give you the control unit with directions to the site.

Easy, free and a fun way to practice using that fancy transceiver you have that will freak you out when you are in a real avalanche situation where your best friend is buried.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 530-9SNO.

December 21 Avalanche Advisory

Mon, 21 Dec 2009 00:00:00 MST
West Central Montana Avalanche Center
Avalanche Advisory
Posted Monday December 21, 2009 at 0600

Good morning backcountry riders and sliders! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for the 2009 Winter Solstice on Monday December 21, 2009.

Current Avalanche Danger

The avalanche danger is HIGH above 7000' on any terrain steeper than 35 degrees that has enough snow to cover anchors. The heavy, dense snow accumulating at the higher elevations is stressing extremely weak basal snow to the point of failure in many locations and on all aspects.

At lower elevations, 5000 to 7000 feet, and in areas where the snow has not yet buried anchors the avalanche danger is MODERATE.

It rained to 6500 feet Sunday with very little snow accumulation during the warm temperatures the past several days. At this mid-range elevation, the snow has either settled out or slid out where deep enough and will set up like concrete once cooler temperatures arrive later this week.

Below 5000 feet, the avalanche danger is LOW.

Weather and Snowpack Analysis

We still have a complex situation mostly at the higher elevations. Many high elevation locations throughout the advisory area do not yet have the depth required to cover anchors and in many cases, the travel getting there is difficult. Anyone that has been out on a sled or skis touring the past few days will verify how tough the off trail travel is under these conditions.

Mountain temperatures have been warm, into the 30's since Thursday, and SNOTEL sites have only picked up .4 to about an inch of snow water equivalent since our last report. Most of the wet weather has been in the northern areas but temperatures have been consistent from SNOTEL to SNOTEL.

At the high elevations, there is 50cm of faceted snow at the ground now protected from these moderate temperatures so this weak snow is going to be with us for several weeks. We were experiencing collapse noises and fracture propagations and getting very low stability test scores while on a tour in the Rattlesnake Sunday.

This YouTube video shows why we are concerned about the future of our snowpack in the higher, steeper ground in the Bitterroots, Rattlesnake, Swan and Mission Mountain ranges.

http://www.youtube.com/watch?v=d2uS709pCG4

It is all about timing, elevation, how much snow a particular location received and if a slab has formed above the faceted snow that formed in early December. Many places did not yet have a slab above these facets last week. Now there is.

Take a little extra time to gather as much information as possible and do not rely on one set of data that proves what you set out to do. I would not want to find myself on any steep open terrain these days. Pay attention to what you see and hear. The steep and deep is dangerous right now.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting a warm moist southwesterly flow with high snow levels. A cold front will push through the area Monday night causing a burst of heavier precipitation. A moist and unsettled pattern will persist through Wednesday.

Expect avalanche conditions to deteriorate if we receive heavy new snowfall. It's going to take several weeks for the weakness at the base of the upper elevation snowpack to gain strength.

We will post the next avalanche advisory on Christmas day.

Transceiver Park Information

There are now 3 Beacon Basin avalanche transceiver parks in operation in western Montana. They are located at Lost Trail Powder Mountain, Lolo Pass Visitor Center and Montana Snowbowl. All three will be available for use for the entire season during operating hours at the ski areas and Lolo Pass Visitor Center.

The Beacon Basin at Montana Snowbowl requires purchase of a lift ticket to access the site located at the backcountry access point to Point Six and is available everyday. If the unit is not there, check in with the ski patrol in the Warming Hut at the top of the Lavelle lift and they will give you the control unit with directions to the site.

Easy, free and a fun way to practice using that fancy transceiver you have that will freak you out when you are in a real avalanche situation where your best friend is buried.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at info@missoulaavalanche.org or call us at 406-530-9766. 406-530-9SNO.

December 18 Avalanche Advisory

Fri, 18 Dec 2009 00:00:00 MST
West Central Montana Avalanche Center
Avalanche Advisory
Posted Friday December 18, 2009th at 0630

Good Morning skiers and riders, this is Steve Karkanen at the West Central Montana Avalanche Center with this first regular backcountry avalanche information advisory for the 2009-2010 season.

Current Avalanche Danger

Above 7000' on any terrain steeper than 35 degrees that has enough snow to cover anchors the avalanche danger is HIGH. Several inches of heavy, dense snow is stressing extremely weak basal snow to the point of failure in many locations and on all aspects. At lower elevations, 5000 to 7000 feet, in areas where the snow has not yet been given the chance to bury anchors the avalanche danger is MODERATE with pockets where the danger is elevated to CONSIDERABLE particularly where wind cross-loaded a steep slope or where ground anchors are not present. Below 5000 feet, the avalanche danger is LOW.

As you can tell from the above statement, we have a complex situation developing. It is all about timing, elevation, how much snow a particular location received and if a slab has formed above the faceted snow that formed in early December.

Weather and Snowpack Analysis

Mountain temperatures warmed and the upper air mass allowed heavy precipitation to move back into the area on the heels of prolonged cold and mostly dry conditions that parked over the area for several days. SNOTEL sites picked up 2.5 to nearly 4 inches of snow water equivalent since the cold weather broke December 11th. That translates to lot of new snow and a heavy load on a very weak base.

Most of our observers reported seeing the classic signs of instability Thursday. whumpfing or collapse noise while traveling, fracture propagation, recent avalanches and a definite warm up with heavy precipitation the past few days. We have also received excellent reports from skiers and riders in the Hoodoo Pass area who saw avalanche activity and the above indicators of unstable conditions.

A word of caution. Many of the sites we like to ski and ride in are not easily accessible or just do not yet have enough snow to ride. Stability testing in some of these areas can give a false sense of security if you perform stability tests in these locations then travel to a spot not far away with a completely different snowpack. Do rely on what the snow tells you as you travel. Our first snowpit was telling us we had a moderately stable snowpack, even when the snow collapsed on approach to this particular site. We also saw evidence of recent avalanche activity on the ride up the mountain. We moved to a new site that was more representative of bigger, open, and loaded slopes to get more info. This is what we found and is truly representative of the bigger picture even though the testing shown on this clip is on flat ground.

http://www.youtube.com/watch?v=aT8KeVxFNy4

Take a little extra time to gather as much information as possible and don't rely on 1 set of data that proves what you set out to do. I would not want to find myself on any steep open terrain these days. Pay attention to what you see and hear. The steep and deep is dangerous right now.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting moderate temperatures without much new snow for the next 2 days. A broad trough of low pressure moves into the Pacific Northwest later this weekend causing widespread precipitation and cooling temperatures.

Expect avalanche conditions to deteriorate if we receive heavy new snowfall. Its going to take several days for this condition to improve.

We will post the next avalanche advisory Monday December 21.

Transceiver Park Information

There are now 3 Beacon Basin avalanche transceiver parks in operation in western Montana. They are located at Lost Trail Powder Mountain, Lolo Pass Visitor Center and Montana Snowbowl. All 3 will be available for use for the entire season during operating hours at the ski areas and Lolo Pass Visitor Center. The Beacon Basin at Montana Snowbowl requires purchase of a lift ticket to access the site that is located at the backcountry access point to Point Six.

December 13 Information update

Sun, 13 Dec 2009 00:00:00 MST
This is Steve Karkanen at the West Central Montana Avalanche Center with an early season avalanche safety information statement.

We are a bit edgy here at the avalanche center with the arrival of our first major winter storm. A lengthy period of cold windy weather at the higher elevations turned the base of our future snowpack into a weak faceted mess.

A winter storm warning has been issued for western Montana with snowfall amounts estimated to be 12 inches to 17 inches above 6000 feet by Monday.

This storm will easily overload an already weak snowpack even at the lower end of the precipitation estimates. Any slope steeper than 30 degrees that receives more than 6 inches of new snow should be suspect until proven otherwise. Wind-loaded terrain will be especially sensitive during this storm cycle so pay close attention to any indicator of instability. This will be a dangerous time to ski or ride on recently loaded slopes steeper than 30 degrees on any aspect. Please keep informed about this storm as it develops.

Average snow depths at the SNOTEL sites in our area are only 20 inches and average temperatures have been well below 20 degrees since the first of the month with a six-day period when temperatures remained below zero with high winds mostly from the east and northeast during this arctic blast.

This cold period with little or no snow accumulation worsened an already weak layer at the ground and grew faceted snow throughout the snowpack. An additional layer of concern is a warm wx or sun crust that formed sometime around Thanksgiving. Some locations have two of these crusts with weak faceted snow above and below these layers.

In addition to the cold temperatures, east winds redistributed snow from the usual leeward east to northeast aspects to west to southwest aspects so expect weak basal snow on all aspects when the first major winter storm arrives.

That storm arrived just as the Montana Grizzlies beat Appalachian State today, 24-17, a great way to bring on the snow!

We have received several excellent reports this past month all of which describe mostly thin early season conditions. The northern Bitterroot Mountains near Hoodoo Pass have adequate snow for the hardcore but even here, the goods have been limited to remote and sheltered wind loaded terrain.

The major red flags or indicators of an unstable snowpack condition are:

Recent avalanche activity- this is the clearest indicator of an unstable snowpack that many people overlook.

Heavy new snowfall or rain- most avalanches occur during or immediately after a storm.

Collapse noises or a whumpfing sound of the snow pack - if you experience this on flat terrain assume unstable conditions on a steeper slope.

Shooting cracks or fracture propagations running out from you as you travel, typically associated with collapse noises.

High winds - any amount of snow with wind can quickly raise the avalanche danger on leeward terrain.

Warming temperatures - a storm that starts out cold and turns warm puts heavy snow on cooler weaker layers.

If you see any of these indicators, the snowpack is unstable.

If you do get out and see any activity or just want to let us know what you see out there, send us a note at info@missoulaavalanche.org. We really appreciate observations from you, it helps us provide better information in our advisories.

We begin issuing regular Friday avalanche advisories on December 18 and regular Monday advisories as soon as the snow begins to accumulate.

Halloween Week Avalanche Information

Tue, 27 Oct 2009 00:00:00 MST
Hello and Happy Halloween!

This is Steve Karkanen at the West Central Montana Avalanche Center with an early season avalanche information statement. It is October 27, 2009 and though we have not seen a lot of early season snow, we clearly have conditions in some isolated areas where avalanches can happen.

This past weekend, on 10/24, 4 skiers in 2 separate groups triggered and were caught in an avalanche on a steep NE facing slope above 9000' near Gem Lake in the Southern Bitterroot Mountains. All went for a ride, were tumbled and banged up but able to recover. One person sustained minor injuries requiring a visit to a local hospital. All were able to extricate themselves and able to walk back to the trailhead under their own power.

Check out this excellent write-up and photos submitted by one of the involved individuals:

Gem Lake - Southern Bitterroots - October 24, 2009

On Halloween, a very similar incident occurred in the Tobbacco Root Mountains NW of Ennis, MT. The Gallatin National Forest Avalanche Center posted an excellent report and photos on their website.

Granite Peak - Tobbacco Roots - Halloween 2009.

These candid narratives reminds us of just how easily we can find ourselves in a life or death scenario at a time of year when avalanches are far from the conscious mind.

Hunters are not immune from this danger and may be more at risk in avalanche terrain than snow riders. Avalanche danger is the furthest thing from a hunters mind. Being armed to the teeth does not prepare one for avalanche risk. Just consider where you travel in the mountains. No snow, no problem. Snow on a steep open slope that has covered up the rocks and beargrass may indeed be a problem.

While we have little or no snow in most mountain locations, terrain above 6000' has received snow and the sheltered aspects are holding it. The brutal cold temperatures we experienced around homecoming weekend (10/10) formed a faceted layer of crystals that were buried in later storms. This appears to be the culprit in the incident last weekend. It will need to be considered wherever early October snow established itself mostly on North aspects above 9000' particularly in wind loaded areas.

Winter 2009-2010 plan.

We plan to begin regular Monday and Friday avalanche advisories starting in mid-December. We will post information statements earlier as needed depending on weather and snow conditions.

We're starting to schedule our winter avalanche training sessions. Stay tuned to our schedule on the education and events page and call us if you are interested in scheduling a class for your organization or group.

Avalanche Transceiver Training Parks

This year we have 3 avalanche transceiver training parks available for interested individuals or groups. They are located at Lolo Pass Visitor Center, Lost Trail Ski Area and Montana Snowbowl. The training parks at Lolo Pass and Lost Trail will be accessible by anyone at no charge. Both are located close to parking. The Snowbowl training park is located at the top of Snowbowl and requires purchase of a lift ticket to access the site.

These beacon parks are the result of partnerships and donations to the West Central Montana Avalanche Foundation by snowmobile clubs, backcountry skiers, search and rescue groups and individuals.

If you get out and have any interesting snow or weather observations you'd care to share, or want more information about upcoming classes, please contact us at info@missoulaavalance.org or call 406-329-3752.

Have a safe Halloween and get ready! The Burning Dog fund raising events seem to work (with two epic winters in a row) and there's no reason to doubt this year will be any different!

missoulaavalanche News Fall 2009

Tue, 13 Oct 2009 00:00:00 MST
Good afternoon. This is Dudley Improta with missoulaavalanche.org news for the upcoming winter. Actually the last week has felt pretty winter-like in Montana. The 2009/2010 snowpack is underway in the high elevations. I would like to draw your attention to some upcoming events and education opportunities.
This Friday the Burning Dog "Pray for Snow Party" is happening at Big Sky Brewery. This has turned into a major fundraiser for the West Central Montana Avalanche Foundation which helps fund the West Central Montana Avalanche Center; which is a lot of words for the advisories and education events that are put on in the name of missoulaavalanche.org.
Be sure to attend and tell your friends about Burning Dog as well as the Warren Miller movie in the Wilma on November 21, another fundraiser.
Then we will move ahead into full on winter with education events: 1-hour avalanche lectures, transceiver classes, Level 1 classes and workshops. Check the education and events section on missoulaavalanche.org.
Generally avalanche advisories will begin around mid-December or perhaps sooner depending on conditions. The Foundation has been working hard getting avalanche beacon parks for Lost Trail Pass and the top of Snowbowl Ski Area. The hope is these two parks will be functional this winter along with the park at Lolo Pass.
Enjoy the fall; look forward to winter.

General Spring Advisory

Fri, 10 Apr 2009 00:00:00 MST
Friday April 10 - 12noon
Good afternoon, this is Dudley Improta with the West Central Montana Avalanche Center. Spring has reluctantly sprung in West Central Montana. I trust you are thinking about river running, fly-fishing, spring ski touring, rock climbing, possibly golf.

The snow generally starts to settle and strengthen at this time of the year, although this week we are hearing about snowmobile triggered avalanches in the Belt Mountains near Helena. During spring and summer timing is the key to avoiding avalanche hazard. Barring a storm laying down fresh powder (which happens) the snow is most likely to be unstable during the heat of the day. Large wet sluffs can be big enough to cause trouble. If it rains you do not want to be on a steep snow slope. So, for spring and early summer backcountry skiing and riding avoid steep open slopes during the heat of the afternoon and don't expose yourself to steep open slopes during or immediately after a rainstorm.

Over the course of the winter Steve and I observed and discussed some questionable backcountry practices. Generally these were poor route finding (in that folks were setting skin tracks across starting zones) and more than one person skiing or riding at a time on the same steep slope. While there are times when starting zones are stable and crossing them is no problem, it sets a poor example for folks who are new to backcountry skiing. Many people may not grasp the subtleties of timing and a calculated risk. Also in areas that are popular people tend to follow the track that is broken. Good route finding is a learned skill and people learn from example. As far as more than one person riding and skiing at a time; it is just a terrible habit to get into. You should never do that. It is estimated there would be 50% fewer avalanche fatalities in Montana if people had followed this one guideline.

I have put some additions on the links page of the website showing beacon and shovel reviews as well as some avalanche accident reviews, if you have time check them out. Steve gave me a very good book to peruse this winter - Deep Survival by Laurence Gonzales. If you do any backcountry or wilderness sports it is worth a read. There are many stories that relate to recreating in avalanche terrain. A reoccurring theme in getting into trouble in the woods is taking a shortcut.

The Avalanche Center has received a lot of support. It would be hard to try to name everyone individually and one would inevitably miss a name but the following individuals and groups are an attempt:
Todd Frank - took over the chair position of the Foundation this year and put in lots of hours and raised a significant amount of coin.
Ross Peterson - maintains the tech portion of the website. We would be dead in the water without his expertise.
Big Sky Brewery - makes the Burning Dog Festival happen, by far the biggest fundraiser.
National Weather Service in Missoula - puts together those awesome backcountry forecasts.
USFS Observers - they go out Thursdays and Sundays and dig holes in the snow instead of skiing or riding.
Public Observers - send us good observations on their own time when touring high in the mountains.
West Central MT Avalanche Foundation Board - all these folks spend some of their precious time raising money and working fund-raising events.
Businesses that buy ads and contribute to Burning Dog - you should patronize them.
The University of Montana Campus Recreation Department - contributes personnel for data collection and advisories and logistical support for classes and presentations.
The Lolo National Forest - sponsors and assumes responsibility for the advisories.

Have a great safe summer, spring and fall.

April 3 Avalanche Advisory

Fri, 03 Apr 2009 00:00:00 MST
Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for April 3, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide below to help you make more informed decisions regarding travel in avalanche terrain for the next few days. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle NF Avalanche Center website.

Weather and Snowpack Analysis

Winter refuses to release its grip on West Central Montana. Most SNOTEL sites received over 2 inches of snow water this past week translating to over 20 inches of new snow. High winds early in the week were moving a lot of snow around and by Wednesday we began hearing of human triggered avalanche activity in the Bitterroot Mountains. The ski patrol at Snowbowl initiated a few large slab avalanches with explosives Wednesday. Temperatures began warming Thursday and most mountain locations reached into the mid to upper 30's. This warming helped further settle the new snow and we were feeling pretty good about stability on all but the steepest terrain. Wind loaded terrain is still spooky but we felt that would also stabilize after a few more hours.

Current Avalanche Danger

All Advisory area locations:
Above 6000 feet the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. Below 6000 feet the avalanche danger is LOW, natural avalanches are very unlikely and human triggered avalanches are unlikely. Please consider that there is a great deal of local variation in snowfall amounts. Even under low to moderate avalanche conditions, you can find isolated pockets of unstable snow on some terrain features especially where wind loaded.

During periods of rapid warming:
The avalanche danger is CONSIDERABLE. Human triggered avalanches are probable, natural avalanches are possible. The first warm day or any amount of rain on all this new snow is going to be a dangerous time to be on or under any steep slope.

Weather Forecast and Avalanche Outlook

An upper trough will allow active convection through the day Friday. Snow showers will be widespread but short lived and not able to produce significant precipitation. Shower activity will begin to diminish Saturday and a warmer ridge will develop over the area Sunday bringing normal to above normal temperatures by the early part of the week.

Expect avalanche danger to improve during the next few days as the snow slowly adjusts to the recent heavy load. During periods of clear weather, pay close attention to how the sun is affecting the snow surface. The sun angle is now high enough that just a few minutes of direct sunlight can warm a slope rapidly enough to bring it down.

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The Beacon Park at Lolo Pass is still available for use but on weekends only. The Lolo Pass Visitor Center is now on their spring operating schedule. Hours are 0800-1630 PDT Saturday and Sundays.

We will no longer issue regular avalanche advisories on Mondays and Fridays. We will post information statements as needed after April 1st.

March 27 Avalanche Advisory

Fri, 27 Mar 2009 00:00:00 MST
Posted Friday March 27th, 2009 at 0600.

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for March 27th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide below to help you make more informed decisions regarding travel in avalanche terrain for the next few days. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle NF Avalanche Center website.

Weather and Snowpack Analysis

Last week we talked about how the warm sunny spring weather was affecting the snowpack, this week we'll backtrack and talk about what a winter storm has done. All SNOTEL sites picked up several inches of moisture starting out as rain last Sunday then turning to snow in abundant quantity by mid-week. Yesterday conditions were more like the end of January with many sites receiving 10-20 inches of new snow the previous 48 hours. Northern locations appeared to be the biggest winners with the Rattlesnake picking up 2.5 inches of SWE (snow water equivalent) in the past week and the Bitterroot Mountains about half as much. This added a lot of weight to what has been a mostly stable snowpack. In some areas, not enough time has passed to allow the snow to adjust to this new load. stability tests were showing mostly stable conditions in the Bitterroot Mountains and somewhat disconcerting conditions in the Rattlesnake.

In the Rattlesnake, we saw several natural slab and sluff avalanches that released during the storm Wednesday night on nearly all aspects. The recent storm winds came from many different directions and all slopes seemed to be treated equally this time around. While touring and skiing we triggered other small slab and loose snow avalanches on all aspects. Anything steeper than 40 degrees was touchy. If you don't have strong skiing and slope assessment skills, it's not a good time to blindly jump into steep terrain. I would expect this condition to persist for the next 24-48 hours or until weather conditions change. The primary concern now is the bond between the new snow and the hard crust that formed earlier in the week. Wind loaded pockets are particularly sensitive. The secondary concern is the weak layer we talked about last week that is now about 85cm or 35 inches deep. Though it takes a lot of force to get it to fail, it fails cleanly with energy and propagates over distance. The culprit is small grained faceted snow that formed on or below a sun crust that formed in late February. I simply wouldn't trust steep shallow areas, rock outcrops, convex slopes or any potential thin spot where it's possible to initiate an avalanche. This type of instability is hard to assess and can lead you into thinking a slope is safe based on high stability scores. And if a slope does fail at that level, it's going to be nasty.

Current Avalanche Danger

Rattlesnake, Southern Swan and Southern Mission Mountains near Seeley Lake: Above 6000 feet, on wind loaded terrain steeper than 35 degrees, the avalanche danger is CONSIDERABLE. Human triggered avalanches are probable, natural avalanches are possible. On all other slopes above 6000 feet the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. Below 6000 feet the avalanche danger is LOW, natural avalanches are very unlikely and human triggered avalanches are unlikely.

Bitterroot Range from Lost Trail Pass to near Lookout Pass:
Above 6000 feet the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. Below 6000 feet the avalanche danger is LOW, natural avalanches are very unlikely and human triggered avalanches are unlikely. Please consider that there is a great deal of local variation in snowfall amounts. Even under low to moderate avalanche conditions, you can find isolated pockets of unstable snow on some terrain features.

Weather Forecast and Avalanche Outlook

A high pressure ridge brought clear skies and cold temperatures to the area Thursday and Friday. Expect warmer temperatures and higher snow levels Friday and Saturday. The next winter weather disturbance is expected to impact mountain locations Saturday night and Sunday with snow reaching valley floors by Sunday morning. Weather models predict significant moisture associated with this fast moving system but the timing is uncertain. The upcoming week will remain moist with below average temperatures under a Northwesterly flow aloft.

Expect avalanche danger to improve during the next few days as the snow slowly adjusts to the recent heavy load. During periods of clear weather, pay close attention to how the sun is affecting the snow surface. The sun angle is now high enough that just a few minutes of direct sunlight can warm a slope rapidly enough to bring it down.

We have received many excellent reports from backcountry snowmobilers and skiers this winter. These informal observations are very valuable to us in that they help us produce a more accurate avalanche advisory. The information you provide may save a life. Many thanks to everyone who sent observations or a quick email to us this winter!

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

We will no longer issue regular avalanche advisories on Mondays and Fridays. We will post information statements as needed after April 1st.

March 20 Avalanche Advisory

Fri, 20 Mar 2009 00:00:00 MST
Posted Friday March 20th, 2009 at 0600.

Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for March 20th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide below to help you make more informed decisions regarding travel in avalanche terrain for the next few days. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle NF Avalanche Center website.

Weather and Snowpack Analysis

Today is the first day of spring and if you ventured into the mountains yesterday you would believe it. It was sunny in the morning and stayed warm throughout the day. Cloud cover moved in by mid-afternoon which will act like a blanket to keep air temperatures warm through the night. Nearly all SNOTEL sites remained above freezing under cloudy skies and only dropped below freezing for a short time last night. These warm temperatures have caused melt water to percolate several inches into the snowpack to a faceted layer associated with a sun crust that formed in late February. This was the weakest feature in the snowpack yesterday in the Rattlesnake and we were able to trigger a 14 inch deep slab on a 40 degree Northeast facing slope with a ski cut. We also received a report of a large slab avalanche that was remotely triggered by snowmachines in Bowl 5 near Sheep Mountain Wednesday.

Observers in the Bitterroot Mountains near Lost Trail Pass and in the Northern part of the range south of Taft, MT report mostly stable snow conditions but noted that warm temperatures will increase instability in these areas as well. All locations were seeing roller ball activity including many North shaded aspects which is a good indicator of instability. The Bitterroot Range received significant snowfall earlier in the week so I would be very suspicious of any steep wind loaded terrain there during the warm weather. The avalanche activity described above is a good example of what can happen when temperatures rise quickly.

Current Avalanche Danger

At all advisory area locations above 6000 feet, during periods when temperatures are above freezing and on terrain steeper than 35 degrees, the avalanche danger is CONSIDERABLE. Dangerous unstable slabs can be found on many steep slopes especially those that have been recently wind loaded. Human triggered avalanches are probable, natural avalanches are possible. On all other slopes above 6000 feet the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. Below 6000 feet the avalanche danger is LOW, natural avalanches are very unlikely and human triggered avalanches are unlikely. You can almost always find isolated pockets where there are dangerous avalanche conditions on some terrain features.

Weather Forecast and Avalanche Outlook

The upper level air flow will be from the Southwest Friday and Saturday resulting in a warmer, moist and unstable atmosphere with shower activity increasing during the afternoon and evening hours. Rain can be expected up to 7000 feet into Saturday. A trough of low pressure is expected to pass over the Northern Rockies Sunday bringing cooler air from the Northwest.

Expect avalanche danger to remain elevated during this period of warmer temperatures. If the higher elevations receive any rain, avalanche conditions will quickly become very dangerous and you don't want to find yourself on or below open terrain steeper than 30 degrees. Once temperatures start to cool down again, the snowpack will be glued together like plywood and will ski about as well.

We have received many excellent reports from backcountry snowmobilers and skiers this winter. These informal observations are very valuable to us in that they help us produce a more accurate avalanche advisory. The information you provide may save a life. Many thanks to everyone who sent observations or a quick email to us this winter!

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be issued Friday, March 27th, 2009. We will no longer (for this season) issue regular avalanche advisories on Mondays. We will post information as needed based on weather and snowpack conditions.

March 16 Avalanche Advisory

Mon, 16 Mar 2009 00:00:00 MST
Posted Monday March 16th, 2009 at 0630.

Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for March 16th, 2009. This will be the last Monday avalanche advisory for this season. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide below to help you make more informed decisions regarding travel in avalanche terrain for the next few days. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis

Mountain temperatures climbed into the forties under bluebird skies Friday and Saturday which left a zipper crust on nearly all but the most heavily shaded slopes. A strong cold front began moving through West Central Montana Sunday bringing gusty winds and moderate to heavy snowfall in some areas above 5000 feet. Not enough snow had been deposited with this system for it to be much of a problem Sunday but we did note that the thin sun crust fails easily with light force. This Bitterroot Mountains are currently receiving the heaviest amount of snow and we did receive a report that the newest snow is moving easily on very steep terrain above 8000 feet. This morning most SNOTEL sites have received several inches of new snow the past 12 hours. Wind speeds on Point Six have been in the 20-30 mph range.

The primary avalanche concern for the next couple of days will be wind slabs that form during this frontal passage. In addition to wind slabs, heavy new snow on the thin sun crust that formed Friday and Saturday will also be a potential safety consideration in areas that receive a foot or more of snow in the next few hours.

Current Avalanche Danger

At all advisory area locations above 6000 feet on wind loaded terrain steeper than 35 degrees, the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. On all other slopes above and below 6000 feet, the avalanche danger is LOW where natural avalanches are very unlikely and human triggered avalanches are unlikely. You can almost always find isolated pockets where there are dangerous avalanche conditions on some terrain features.

Weather Forecast and Avalanche Outlook

A moist Pacific storm is currently moving through the Northern Rockies. Moderate to heavy snow will occur along with strong gusty winds ahead of, with and behind the cold front. Winter weather advisories have been issued for the mountains of Western Montana. Weather models are predicting a more zonal upper level flow for the next few days with Pacific moisture feeding into this flow for continued mountain snow showers. Significant moisture is not expected during this time frame.

Expect avalanche danger to increase during periods of heavy snowfall and high winds. We're beginning to see more spring like conditions in the mountains which means we can go from 4 degrees to 40 in just a few hours or go from skiing and riding melt-freeze corn snow to knee deep powder overnight. Just remember that snow does not like rapid change of any sort so as conditions change we also need to adjust our assessment of just how strong a particular slope is.

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The avalanche danger scale is undergoing revision and your input is desired! This is the last week the survey will be available so take a few minutes to weigh in. It only takes about 10 minutes, is kind of fun and you may even win a prize!

Avalanche Danger Scale Survey

The next avalanche advisory will be issued Friday, March 20th, 2009. We will no longer (for this season) issue regular avalanche advisories on Mondays. We will post information if needed based on weather and snowpack conditions.

March 13 Avalanche Advisory

Fri, 13 Mar 2009 00:00:00 MST
Posted: 06:30
Good morning. This is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for March 13, 2009. This information is the responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight, but the advisory can provide valuable information for evaluating avalanche hazard for the next 48 hours. The advisory area includes the Bitterroot Mountains from Lost Trail Pass to Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Detailed avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis
Our region received modest amounts of snow since Monday morning. The SNOTEL site at Lolo Pass indicated 4.5 inches of snow Monday and Tuesday, other data showed very little snow elsewhere. We did have lots of wind from different directions and frigid temperatures. The cold light-density snow from Sunday through Tuesday was moved around by the wind and left wind slabs up above timberline. During field observations yesterday small skier-triggered slabs were noted as well as skier-triggered sluffing. The wind has also helped solidify the newer snow and, other than the wind slab formation and sluffing, reports from observers are indicating generally stable conditions.
On Northerly aspects we are still seeing a layer of surface hoar that formed the first week of February in some stability tests. This layer has about 30 inches of snow on it and continues to shear cleanly, but it takes a lot of force. Observers from Lost Trail Pass have been observing this layer for weeks and yesterday noted that it was not reacting to stability tests on Northwest slopes.
Right now, the main consideration is wind slabs that have formed above timberline on steep exposed slopes. These wind slabs can be found on the lee sides of ridge-tops and cross loaded in gullies or couloirs.

Current Avalanche Danger
On all slopes above timberline 35 degrees or steeper that are wind-loaded the avalanche danger is MODERATE. Natural avalanches are unlikely and human triggered avalanches are possible. Elsewhere in the region the avalanche danger is LOW. Natural and human triggered avalanches are unlikely.
Do not let our recent string of generally stable conditions lull you into complacency. Continue to practice good travel habits. Go one at a time, skiing or high-marking. Communicate with your travel companions and set safe routes and traverses when negotiating steep terrain.

Weather Forecast and Avalanche Outlook
It looks like a snow-producing system will move in late Saturday and persist through Sunday. The system may favor the Bitterroots with up to 5 inches of snow. Moderate winds are expected on Sunday.
Although we have already experienced some spring-like days this winter it's time to start treating the backcountry snow in a late-season manner. Be aware of rapidly warming temperatures on South and West slopes in the afternoon as March progresses. The snow becomes more sensitive when it warms up quickly.

If you have snow observations or any snow information you'd like to share please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be issued on Monday, March 16, 2009.

The avalanche danger rating scale is being revised. The opinion from folks who use the advisories is important. Please take time to fill out the avalanche danger rating survey.

March 9 Avalanche Advisory

Mon, 09 Mar 2009 00:00:00 MST
Posted: 07:00
Good morning. This is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for March 9, 2009. This information is the responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. But, the advisory can provide valuable information for evaluating avalanche hazard for the next 48 hours.
The advisory area includes the Bitterroot Mountains from Lost Trail to Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Detailed avalanche information about the St. Regis Basin can be found on the .Idaho Panhandle National Forest Avlanche Center website.

Weather and Snowpack Analysis
We received more snow in the region since Thursday. The scenario was good for general stability. The snow associated with the storms on Thursday came in with relatively warm temperatures and temperatures have progressively gotten colder in the mountains since then. The warmer snow seems to have bonded well and the snow from Sunday was very cold, light density snow. Something that did happen this weekend is what the Weather Service refers to as banding. Banding is short periods of very intense snowfall in a local area. Specific areas picked up as much as 7 to 8 inches of snow early Sunday morning. This new snow was readily sluffing on steep aspects naturally and from human triggers. A large enough sluff can knock a person over or push them into rocks or trees. The Rattlesnakes was one of the areas hit by the banding of snow. I toured there yesterday and noted no obvious signs of instability other than the sluffing. My pit tests did reveal that that we still have crusts buried in the snowpack. Hard melt-freeze crusts on southerly aspects and deeper crusts from late January and early February on Northerly aspects can still be found. It takes a lot of force for the snow to react on these layers, but they are still with us. It is worth checking the snow with a quick snow pit before committing to a steep slope. The other thing to pay close attention to is wind loading. As I mentioned the newer snow is very cold and light and will be easily transported by the wind.

Current Avalanche Danger
On all slopes above 6000 feet and 35 degrees or steeper the avalanche danger is MODERATE. Natural avalanches are unlikely and human triggered avalanches are possible. Below 6000 feet the avalanche danger is LOW. Natural and human triggered avalanches are unlikely.

Weather Forecast and Avalanche Outlook
The chances for snow will increase today and this evening and continue into Tuesday. Drier and much colder air is expected after this. It looks like the winds may come from different directions during these changes so pay close attention to local wind loading. Remember this cold snow will move easily with the wind increasing the chance of wind slab formation.

If you have snow observations or any snow information you'd like to share please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be issued on Friday, March 13, 2009.

The avalanche danger rating scale is being revised. The opinion from folks who use the advisories is important. Please take time to fill out the avalanche danger rating survey .

March 6 Avalanche Advisory

Fri, 06 Mar 2009 00:00:00 MST
Posted Monday March 6th, 2009 at 0630.

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for March 6th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis

Since our last report Monday, mountain weather conditions have gone from sunny and warm Monday to cloudy, rainy and warm mid-week to more winter like Thursday. Temperatures associated with a cold front moving through the area dropped allowing all the heavy precipitation embedded within the clouds to fall out as snow which has been heavy at times in some locations. SNOTEL sites report several inches of new snow since Thursday with the Lookout Pass area receiving the most at 17 inches, Lolo Pass 10 inches, Saddle Mountain 8 inches and Stuart Peak 4 inches. Anemometers on Point Six were registering wind speeds in the 40 mile per hour range from the West-Southwest yesterday, but are showing mostly light winds at 5-8 mph this morning. Temperatures are in the teens at most SNOTEL sites.

Observers Thursday all reported that the newest snow is bonding well to the hard snow surface and stability testing indicates a mostly stable condition in all areas with a few notable exceptions. The biggest exception of course is the fact that we all looked at the snow Thursday just as the winter storm entered the area. In areas that received 8 to 10 inches of new snow and wind overnight, I expect stability conditions to be elevated especially on steep wind loaded terrain above 7000 feet. The best assessment of avalanche conditions will be your own so you really need to be paying attention this weekend. High winds, heavy new snow, collapse or cracking of the snowpack, rapid warming and recent avalanche activity are the biggest clues of an unstable condition so be looking for any of these while you're out looking to put fresh tracks on a steep slope.

The other concern are isolated pockets of weak faceted snow that formed several weeks ago that are now deeply buried. The warm weather during the past week helped settle and stabilize these layers on the more exposed slopes but we're still noting failures with energy and ability to propagate fracture on East aspects at mid-slope. These areas appear to be most prevalent in sheltered pockets low on the slope. It takes a lot of force to produce failure in these locations and they are not widespread but certainly worth checking out in areas that haven't seen much traffic.

Current Avalanche Danger

At all advisory area locations above 5000 feet on wind loaded terrain steeper than 35 degrees, the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. On all other slopes above and below 5000 feet, the avalanche danger is LOW where natural avalanches are very unlikely and human triggered avalanches are unlikely. You can almost always find isolated pockets where there are dangerous avalanche conditions on some terrain features.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting a vigorous arctic front to move South near the I-90 corridor this morning. East to Northeast winds of 30 to 40 mph are associated with this frontal boundary but are expected to taper off by Friday afternoon. A shortwave ridge of high pressure will move over the area late Friday bringing partial clearing and a very cold night. Another weather system moves into the area Saturday through mid-week with cooler temperatures and precipitation the bulk of which is expected early Sunday. After this frontal passage, snowfall will become convective with most of the precipitation expected over higher terrain.

As mentioned earlier, the above avalanche danger is based on conditions seen Thursday during the early stage of the storm currently over our area. Expect avalanche conditions to worsen especially on wind loaded terrain during this storm passage. It doesn't look like there is a lot of snow expected at this time but the wind will determine where avalanches can be triggered and will be the biggest factor to consider this weekend.

We've been receiving many excellent reports this winter from many different locations within our advisory area. We try to cover approximately 1800 square miles of terrain in West Central Montana so these reports are of great value in that they help fill the gaps for us. Great job and thanks for sending them in!

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The 5 level avalanche danger scale is being revised for next winter. In an effort to ensure a successful revision, please take the time to complete the following online survey:

Avalanche danger rating survey

The next avalanche advisory will be issued Monday, March 9th, 2009.

March 2 Avalanche Advisory

Mon, 02 Mar 2009 00:00:00 MST
Posted Monday March 2nd, 2009 at 0600.

Good morning backcountry travelers. This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for March 2nd, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. Expect avalanche conditions to change as weather conditions change. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis

Moderate mountain temperatures and light winds since last Friday helped quickly settle the heavy snow we received last week. Temperatures at SNOTEL sites were all well above the freezing point Sunday with the Twin Lakes SNOTEL in the Southern Bitterroot reporting 55 degrees, North Fork Jocko 51 degrees and Stuart Peak at 46 degrees at 1PM. As you would expect with those high temperatures, East to South aspects were rapidly warmed which resulted in many roller balls and a few point release wet snow sluffs coming off the steeper slopes. As soon as it clouded over and cooled this process stopped but you can expect a nasty sun crust on all but the most deeply shaded aspects the next time you get out.

We received reports this weekend from the Bitterroot Mountains and the Rattlesnake all of which indicated a mostly stable condition. Stability testing in these locations was showing that the new snow was failing at the crust that formed prior to the new snow last week but only after a great deal of force was applied to an isolated column of snow. Backcountry skiers in the Southern Swan reported variable conditions with isolated whoomping and a small slab releasing on steep North and East facing slopes involving the newest storm snow.

Current Avalanche Danger

At all advisory area locations above 5000 feet, the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. Below 5000 feet, the avalanche danger is LOW where natural avalanches are very unlikely and human triggered avalanches are unlikely. You can almost always find isolated pockets where there are dangerous avalanche conditions on some terrain features.

On sun exposed slopes during the heat of the day expect wet slab avalanche danger to increase to CONSIDERABLE when temperatures climb above the freezing point. Good indicators of potential wet slab avalanche activity are roller balls and small point release loose snow avalanches originating from rocks or trees. When the snow starts feeling like its rotten, its time to move to a cooler or more shaded location.

Weather Forecast and Avalanche Outlook

A Pacific weather system remains off the Northwest coast keeping a warm moist Southwest upper level flow over Western Montana. The jet stream associated with this system will move through the area tonight increasing mountain winds and keeping snow levels at about 6000 feet. As the Pacific weather system moves East toward Oregon late Tuesday more widespread precipitation will enter Western Montana.

We're starting to go through melt freeze cycles on the south half of the compass which will help to further strengthen the overall stability. The weather forecast is calling for a chance of moisture to enter the area this week so be watching for where and what type of moisture we receive. Any rain on the current snowpack above 5000 feet will be immediately dangerous. Also avoid steep open slopes on the warm afternoons when roller balls are coming off the hill and you're sinking up to your boot tops in wet snow.

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be issued Friday, March 6th, 2009.

February 27 Avalanche Advisory

Fri, 27 Feb 2009 00:00:00 MST
Posted Friday February 27th, 2009 at 0600.

Hello backcountry riders and sliders! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for February 27th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. Expect avalanche conditions to change as weather conditions change. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle Forest Avalanche Center website.

Weather and Snowpack Analysis

After a lengthy period of little or no snow, our mountains received abundant snowfall this week reminding us that it is still winter. Bitterroot Mountain SNOTEL sites recorded an average of 2 inches of snow water equivalent (SWE) while Stuart Peak and the North Fork Jocko SNOTEL recorded 1.5 inches of SWE. Saddle Mountain SNOTEL was the loser with only .7 inches, Hoodoo Basin SNOTEL piled up 3.3 inches of SWE. In other words, we were dumped on!

This snow came in warm and heavy which is good because it appears to have bonded quickly to the hard surface that formed during the sunny warm weather last weekend. All our observers reported dangerous avalanche conditions on some terrain features but not as bad as you would have expected given the set up we had. During and immediately after the initial storm on Tuesday and Wednesday conditions were very sketchy as the old snow was getting loaded quickly and heavily putting a great deal of stress on a couple of weak layers. We have been talking about buried crusts and faceted snow associated with those crusts for a few weeks now. These layers of concern are the sun crust that formed last weekend, the crust and facets that formed around Groundhog Day and the significant melt-freeze crust and facets that formed around Martin Luther King Day.

We received an outstanding report and some excellent photos of this very situation from John Lehrman in the Bitterroot Mountains near Downing Mountain. Check it out on John's website backcountryfocus.com .

All our observers described very similar conditions regarding the new snow. It has bonded well to the old snow surface, it takes a lot of force to get it to fail, it does not fail cleanly nor with energy but when it fails it fails at the thin faceted crust layer that formed in early February and it is a big slab. You don't want to get caught up in something this big. So the recommendation is to take it easy for a couple of days to give the new snow a chance to settle out and give these crusts some time to glue together.

Current Avalanche Danger

In the Bitterroot Mountains above 5000 feet on terrain steeper than 35°, the avalanche danger is CONSIDERABLE. Dangerous unstable slabs can be found on many steep slopes especially those that have been recently wind loaded. Human triggered avalanches are probable, natural avalanches possible.

At all other locations above 5000 feet in West Central Montana, the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. Below 5000 feet, the avalanche danger is LOW where natural avalanches are very unlikely and human triggered avalanches are unlikely. You can almost always find isolated pockets where there are dangerous avalanche conditions on some terrain features.

The Bitterroot Range received the most precipitation this week but keep in mind there may be pockets of considerable avalanche danger in the Rattlesnake and in the Southern Mission and Swan Ranges near Seeley Lake.

Weather Forecast and Avalanche Outlook

Snowfall has tapered off this morning and we can expect a few lingering showers over the mountains for the next few hours. Winter storm warnings have expired but winds may still be an issue at the highest elevations. A ridge of high pressure will build over our area Friday night into Saturday with another weather system expected to enter the area Sunday and Monday. Temperatures may drop into the single digits early Saturday under clear skies then again climb back into the 30 degree range for the weekend.

Expect conditions to improve unless we undergo rapid warming under clear skies or receive rain on this newest snow. High winds will also contribute to instability on steep leeward terrain.

The past few weeks we've enjoyed a very stable snowpack and conditions that allow us to travel into terrain that was impossible to get to during the New Year. Now that we're getting the snow we dream about and can get to the big lines, we need to step or throttle it back, be a little extra cautious, take a little more time to fully assess stability conditions on the particular slope you want to jump into before committing yourself and others. Then when you decide to do it, do it one at a time. Always!

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be issued Monday March 2nd, 2009.

February 23 Avalanche Advisory

Mon, 23 Feb 2009 00:00:00 MST
Posted: 07:00
Good morning. This is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for February 23, 2009. This information is the responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. But, the advisory can provide valuable information for evaluating avalanche hazard for the next 48 hours.
The advisory area includes the Bitterroot Mountains from Lost Trail to Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. For specific avalanche information about the St. Regis Basin visit the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis
Snotel sites in the region are showing significant settlement of the snowpack since Friday. Settlement of the snow generally indicates stability. The moderate danger we talked about Friday has diminished this weekend with warm temperatures and no precipitation. There has been some surface hoar formation that wasn't destroyed by the sun on North aspects. Many folks we communicated with reported good skiing and riding conditions on Northerly aspects at elevations above 6000', where the snow remained cold. No doubt we have developed yet another melt-freeze crust on Southeast/South/Southwest aspects from this weekend of balmy weather. So, we'll be paying attention to surface hoar layers on the Northerly aspects and crusts on the Southerly aspects as possible future weak layers or sliding surfaces.

Current Avalanche Danger
As of Monday (2/23/09) morning the avalanche danger in the region is LOW. Natural and human triggered avalanches are unlikely. MOSTLY safe conditions exist. LOW avalanche danger does not mean NO avalanche danger. There are always isolated pockets of instability in the snowpack. These kinds of conditions would mainly be on high exposed ridges with wind deposits or on steep slopes with exposed rock outcrops.

Weather Forecast and Avalanche Outlook
It looks like (hopefully) some snow will head our way in the next couple of days. Snow will be widespread, but light, until Monday night and Tuesday. Still only moderate accumulations are expected (but we'll take it). The chances for snow increase into Tuesday and Wednesday. If we get the new snow that is predicted expect the avalanche danger to go to MODERATE on slopes above 6000' that are 35 degrees or steeper. Natural avalanches will be unlikely, human triggered avalanches will be possible.

If you have snow observations or any snow information you'd like to share please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be issued on Friday, February 27, 2009.

February 20 Avalanche Advisory

Fri, 20 Feb 2009 00:00:00 MST
Posted Friday February 20th, 2009 at 0600.

Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for February 20th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. Expect avalanche conditions to change as weather conditions change. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle Forest Avalanche Center website.

Weather and Snowpack Analysis

Most mountain locations received a trace of precipitation since Sunday with the Northern portion of the advisory area receiving the most snow. North Fork Jocko SNOTEL received .80 inches of snow water equivalent or about 6-8 inches of snow. Most of the other sites received 3-4 inches since Sunday. Mountain temperatures were in the mid thirties for highs and in the teens for lows.

In Monday's advisory I discussed a persistent weak layer that hasn't been much of a problem because it did not have a slab above it. Wind, warmer temperatures and a bit more snow have formed a slab above this weak layer and it fails on steeper slopes with the right kind of force applied. We've received excellent reports from several different locations in the Bitterroot Mountains, Sheep Mountain and the Rattlesnake which described similar weakness and potentially dangerous avalanche conditions with the next big storm. This is perhaps best illustrated by the YouTube clip from our tour in the Rattlesnake Wilderness on Thursday. This appears to be a widespread condition above 7000' on East to North aspects in West Central Montana.

February 19 Rattlesnake Rutschblock stability test.

Current Avalanche Danger

Above 6000' on wind loaded terrain steeper than 35°, the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. All other slopes have a LOW avalanche danger where natural avalanches are very unlikely and human triggered avalanches are unlikely. You can almost always find isolated pockets where there are dangerous avalanche conditions on some terrain features.

Weather Forecast and Avalanche Outlook

A ridge of high pressure will build over the region Friday bringing a warming and drying trend to the mountains with valley inversions and fog setting up over the lower terrain. A moist Pacific system will approach our area Sunday night with warm air and widespread precipitation. Snow levels are expected to be between 5000' and 6000' on Monday.

It doesn't appear that we'll see significant snow at least for the next few days. The predicted warm weather (into the mid-forties at high elevations Saturday) should help stabilize the persistent weak layers we're worried about. Expect avalanche conditions to improve for the next few days. Wet snow avalanches may be a concern on the Southern aspects during sunny days. These will initially involve the surface snow but once wet and heavy snow starts moving it can overload more deeply buried weaknesses all the way to the ground. Remember, we still have mature facets (depth hoar) at the ground in most locations.

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

Dudley Improta will issue the next avalanche advisory Monday February 23rd.

Presidents' Day Avalanche Advisory

Mon, 16 Feb 2009 00:00:00 MST
West Central Montana Avalanche Center
Avalanche Advisory
Posted Monday February 16th, 2009 at 0600.

Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for Presidents' Day, February 16th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. Expect avalanche conditions to change as weather conditions change. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle Forest Avalanche Center website.

Weather and Snowpack Analysis

This report will be mostly a repeat of what we said last Thursday. Mountain locations have not received any significant weather the past 3 days and temperatures have remained cool and consistent even during the sunny days. I was touring in the Rattlesnake Sunday and saw that people are skiing steep lines with abandon with only minor surface sloughing occurring.

The buried surface hoar and facets that formed on a sun crust several days ago is persisting with the cooler weather but there really isn't a slab above it to worry about. The main thing to watch for now will be wind slabs forming on the steeper terrain. As soon as we start receiving significant snow expect the surface to start moving as the buried facets fail to support a heavy new load.

Current Avalanche Danger

At all advisory area locations above 6000' on wind loaded terrain steeper than 35°, the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. All other slopes have a LOW avalanche danger where natural avalanches are very unlikely and human triggered avalanches are unlikely. You can almost always find isolated pockets where there are dangerous avalanche conditions on some terrain features.

Weather Forecast and Avalanche Outlook

A series of weak Northerly storm systems will bring a chance of snow to the Mountains of Western Montana Sunday night and then again Tuesday. No significant snow accumulation is expected during any of these events.

Expect avalanche conditions to continue to improve for the next few days. A significant new load on steep slopes from wind or storm snow will quickly raise the avalanche danger to considerable or high in areas where the above described weakness exists. Also keep in mind that many of the sheltered lower elevations that were in the fog during the inversion 2-3 weeks ago have an obvious buried surface hoar layer that will become reactive with a new load. This is most pronounced in the Lolo Creek drainage at elevations below 5000'.

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted on Friday, February 20th, 2009.

February 13, 2009 Avalanche Advisory

Fri, 13 Feb 2009 00:00:00 MST
Posted Friday February 13th, 2009 at 0600.

Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for February 13th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. Expect avalanche conditions to change as weather conditions change. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis

During the past 4 days all mountain locations received very light snowfall and experienced diminished winds. Observers report good skiing and riding conditions and continued strengthening of the deeply buried facets we have been talking about since December. We received several excellent reports from skiers and riders in the Bitterroot and on Wisherd Ridge (near Sheep Mountain NE of Missoula) all of whom reported loose snow avalanching on steep open slopes. This activity is occurring on slopes steeper than 40° and is involving the newest storm snow, which in most areas is less than about 8". It fails on the interface of the new snow and faceted crystals or surface hoar on a prominent sun crust that formed several days ago. Some isolated locations, such as Wisherd Ridge, appear to have received a bit more snowfall (up to 14") and have more potential for a soft slab already set up on this weak layer.

This will be a serious avalanche problem once a slab forms. The ease of the new loose snow failing on these facets is a huge indicator of what's to come when we receive several inches of heavy snow or high wind. At this point, all we really need is a high wind to lay down a stiff wind slab on the weaker (and now protected) surface hoar and facets associated with the upper level crust.

Current Avalanche Danger

At all advisory area locations above 6000' on wind loaded terrain steeper than 35°, the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. All other slopes have a LOW avalanche danger where natural avalanches are very unlikely and human triggered avalanches are unlikely. You can almost always find isolated pockets where it is possible to trigger an avalanche with the right amount of force, but why would you want to do that?

If temperatures warm up that alone will turn this light snow into a slab that is just thick enough to be dangerous. Right now, it's really not much of a problem unless you're in terrain where you could get knocked over a cliff or pushed through trees on a steep slope. Just be aware of this and don't take any chances if you're not an accomplished rider or skier.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting a weak upper level flow through the weekend with a large upper level trough dominating the weather pattern for the Western US. Any significant moisture and instability will pass well south of our area through the weekend.

Expect avalanche conditions to remain similar and to slowly improve for the next few days. A significant new load on steep slopes from wind or storm snow will quickly raise the avalanche danger to considerable or high in areas where the above described weakness exists. Also keep in mind that many of the sheltered lower elevations that were in the fog during the inversion 2-3 weeks ago have an obvious buried surface hoar layer that will become reactive with a new load. This is most pronounced in the Lolo Creek drainage at elevations below 5000'.

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted on Monday, February 16th, 2009.

February 9 Avalanche Advisory

Mon, 09 Feb 2009 00:00:00 MST
Posted: 07:00
Good morning. This is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for February 9, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. But, the advisory can provide valuable information for evaluating avalanche hazard for the next 48 hours.
The advisory area includes the Bitterroot Mountains from Lost Trail to Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Detailed avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis
West Central Montana received some snow Friday and Friday evening. The storm mainly put down snow in the Northern part of the forecast area. The Hoodoo Basin Snotel registered 8 inches, the Rattlesnake got about 5 inches, about 3 inches at Lolo Pass, a trace at Lost Trail pass; the North Fork of the Jocko and the Seeley Lake region came in the winner with 9 inches of new snow. After our brief flirtation with winter we returned to high pressure, warm temperatures at altitude and a mild inversion. There was not a lot of wind associated with the snow or with the following high pressure. Winter returned this morning and Snotel sites are showing accumulations from Sunday night; 1.5 inches in the Rattlesnake to a trace near Lost Trail Pass. Yesterday and Saturday observers reported the new snow sluffing on steep slopes. This snow is moving on steep, open slopes above 6000 feet. In some areas the snow is moving and accumulating up to a foot in depth. Generally the slopes are stable, but on large open bowls above 6000 feet on steep slopes the snow is moving when skied. These observations are related to the Northern part of the forecast area (Rattlesnakes, Seeley Lake) where we received more snow. We were sent a photo of a low elevation avalanche (below 5000 feet) near the Seeley Lake area. This slide appeared to have run this weekend during the heat of the day on surface hoar that developed during the clear nights last week. This photo can be viewed on missoulaavalanche photos .

Current Avalanche Danger
In the Northern Bitterroot, the Rattlesnakes and the Seeley Lake areas on slopes 35 degrees and steeper the avalanche danger is MODERATE. Natural avalanches are unlikely and human triggered avalanches are possible. Elsewhere in the forecast region the avalanche danger is LOW. Natural avalanches and human triggered avalanches are unlikely.

Weather Forecast and Avalanche Outlook
It looks like over the next couple of days two weak pacific systems will be passing through the Northern Rockies. Areas most likely to see moderate snow will be the mountains adjacent to the Idaho border. Some areas may receive 3 inches of new snow today and winds up to 20 mph are predicted for Tuesday. There were observations of significant surface hoar development from Saturday night; if you recreate where there is new snowfall and/or wind-blown snow keep in mind it may have fallen on this weak layer.

If you have snow observations or any snow information you'd like to share please contact us at info@missoulaavalanche.org .

Steve Karkanen will issue the next avalanche advisory on Friday, February 13, 2009. We did not draw straws to see who would issue the advisory on Friday the 13th, Steve volunteered.

February 6 Avalanche Advisory

Fri, 06 Feb 2009 00:00:00 MST
Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for February 6th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. Expect avalanche conditions to change as weather conditions change. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis

Mountainous locations in West Central Montana received very little precipitation the past 4 days. Afternoon temperatures reached into the 40's and low 50's in some locations as clear skies and sunny days ruled. Winds were SW in the 20's and have turned more Easterly last night as a minor weather system entered into the area. Our overall snowpack continues to strengthen with the moderate temperatures however all our observers were reporting a weak layer about 6" under the surface. This weak snow is associated with a buried surface hoar layer and facet growth that is occurring above and below a crust that formed several days ago. Some areas are seeing surface hoar growth in isolated pockets. These features are not currently a problem but will need to be treated with suspicion once we receive a few inches of new snow and wind.

Our current snowpack is now excellent for travel, not so good for skiing and the top few inches a perfect avalanche bed. All we need is a big dump of snow and things will start getting tricky. Keep informed on current and expected weather conditions.

Current Avalanche Danger

At all advisory area locations the avalanche danger is LOW. Natural avalanches are very unlikely, human triggered avalanches are unlikely. In isolated areas that have been recently wind loaded, the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. Unstable slabs may be found on leeward terrain steeper than 35° above 5000'.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting a weak upper level storm from the Southwest US to bring accumulating snow to the mountains of West Central Montana starting early Friday and continuing through Saturday. The Bitterroot Mountains and the Bob Marshall areas appear to be the most favored for accumulating snow.

Expect avalanche conditions to worsen in areas that receive significant new snow and wind. 6" to 10" of new snow with wind will bring the above mentioned weaknesses to life. Look for and pay attention to clues that shout "I'm unstable!" These are recent avalanche activity, heavy new snow, high winds, whumpf noises, shooting cracks or collapse of the snow underfoot.

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted on February 9th, 2009.

February 2, 2009 Avalanche Advisory

Mon, 02 Feb 2009 00:00:00 MST
Posted: 07:00
Good morning. This is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for February 2, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight.
The advisory area includes the Bitterroot Mountains from Lost Trail to Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Detailed avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis
Some areas in West Central Montana received a bit of snow in the last 24 hours, but not very much. We did, however, get a lot of strong winds on Saturday. Gusts on Point Six in the Rattlesnakes were consistently recorded at 40-50 mph on Saturday. Generally, the snow from last week has bonded well to the melt freeze / sun crust that formed during mid-January. We did receive a report that this snow was not well-bonded in the central Bitterroots, but that snow was very loose and had not formed a slab. Another report from the St. Regis Basin area noted the heavily wind loaded areas and some shooting cracks on these areas. Reports from Lolo Pass and Lost Trail Pass indicated a stable snowpack but noted wind deposits from Saturday. We observed a very stable snowpack in the Rattlesnakes yesterday with a lot of evidence of high winds. In fact, I skied in the Rattlesnake backcountry Saturday and the wind was fierce.
Keep in mind that wind is a major architect of avalanches; so even with trace amounts of new snow do not discount any wind-loaded areas above tree-line. Ridge-tops with wind deposits or cross-loading in gullies would be hazards to look for. When the winds calmed down surface hoar did develop on many slopes Saturday night. A surface hoar layer always bears attention as a possible future weak layer.

Current Avalanche Danger
On any wind-loaded slopes above tree-line the avalanche danger is MODERATE, natural avalanches are unlikely and human triggered avalanches are possible. Elsewhere in the region the avalanche danger is LOW, natural avalanches are unlikely and human triggered avalanches are unlikely. LOW avalanche danger does not mean no avalanche danger; pockets of unstable snow may exist in some terrain features.

Weather Forecast and Avalanche Outlook
There may be some modest accumulation of snow today with a high pressure ridge moving into the Northern Rockies tonight and into Tuesday. This high pressure may allow for valley inversions to establish over the area, which means the higher elevations will see seasonably high temperatures. These high temperatures should help stabilize the snowpack and possibly break down surface hoar formation on Southerly and Westerly slopes. The high pressure should break down toward the end of the week. The next snow is predicted for Sunday night.

If you have snow observations or any snow information you'd like to share please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be issued Friday February 6, 2009.

Steve Karkanen and I will be presenting an avalanche awareness class at the University of Montana. The class has two evening sessions. The first session is tomorrow night at 7pm in the North Urey Underground Lecture Hall.

January 30, 2009 Avalanche Advisory

Fri, 30 Jan 2009 00:00:00 MST
Posted Friday January 30th, 2009 at 0600.

Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for January 30th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can expect avalanche conditions to remain similar unless weather conditions change significantly. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis

Most mountain locations received a few inches of new snow since Sunday with a few Bitterroot mountain locations picking up close to 15". Temperatures started to moderate from the negative and single digits back up into the twenties on Thursday. Winds have been strong from the SW and have been moving snow as soon as it falls. Surface conditions range from several inches of blower powder in the sheltered pockets to hard scrabble where wind has scoured open terrain.

All observers are reporting the new snow is failing on the sun crust but it is not yet a significant problem. We're seeing easy failures on this crust but they do not snap out of the pit with energy and the shear plane is rough meaning it is bonding fairly well to this hard surface. There are near-surface-facets just beneath the crust and many areas had ample opportunity for surface hoar development during the cold clear weather that ended last week. Locations near the transition from fog to clear (elevations up to 5500') have a surface hoar layer that is now buried and needs to be watched. These are tricky and can be a big surprise after skiing all day at higher elevations with no sign of instability. Watch for this on lower terrain in drainages where the fog persisted last week or wherever there is open running water.

The factors to watch for now are how well the new snow bonds to the hard surface; how much weight will the sun crust support; and can we trust the weak faceted snow at the ground? So our worries are features close to the surface and the mature depth hoar now deeply buried at the ground in some areas. The former is more of an immediate concern than the latter but it all depends on how much weight and how quickly it is added to our current snowpack. Areas where the snow is thin are not to be trusted regardless of how much snow we get.

Current Avalanche Danger

At all advisory area locations above 5000' the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. Unstable slabs may be found on steep terrain. Below 5000' the avalanche danger is LOW. Natural avalanches are very unlikely, human triggered avalanches are unlikely. Dangerous avalanche conditions exist in isolated areas where the snow is thin. These are typically found on West, South and East aspects, in rocky areas or where wind has scoured the snowpack. It takes a lot of force to produce failure of the snowpack in these areas, but it fails to the ground on the faceted snow that formed in December.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting significant snowfall in Western Montana from early Saturday through early Sunday. Wind will be a factor as the pressure gradient is expected to increase at the surface.

Expect avalanche conditions to worsen in areas that receive significant new snow and wind. Conditions Thursday were mostly safe but it won't take much snow with high winds moving it around to bump the avalanche danger into the considerable range.

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted on Groundhog Day, 2009.

January 26 Avalanche Advisory

Mon, 26 Jan 2009 00:00:00 MST
Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for January 26th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can expect avalanche conditions to remain similar unless weather conditions change significantly. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis

Last week's warmer temperatures followed by this weekend's quick cold snap have helped further stabilize the more worrisome features we've been addressing the past few weeks. With each passing day, it continues to get more difficult to produce failures during our stability testing. If you like sliding on concrete, this is the time for you to get out!

We received good information from backcountry riders in the Southern Bitterroot who indicated stable conditions and faceted snow growth at the surface. As mentioned last week, this feature needs to be considered during the next big storm. We've also been receiving reports from locations that were near last week's inversion transition zone. These locations saw significant surface hoar growth (due to the higher humidity) while the higher (and warmer/drier) elevations were too dry to allow SH development.

As far as the rotten snow at the ground is concerned, we've been talking about this all winter and it just isn't going away anytime soon. The warmer weather helped glue things together now that it's cold again but those facets at the ground are pretty well insulated and remain a concern on some slopes. Areas that have shallow or thin snow cover are the most susceptible to failure at this level but it takes a lot of force. We were only able to produce failures on pockets of shallow snow (less than 100cm) on East and West aspects.

You can view 2 good examples of this on these YouTube videos:

Video 1

Video 2

Current Avalanche Danger

At all advisory area locations the avalanche danger is LOW. Natural avalanches are very unlikely, human triggered avalanches are unlikely. Low avalanche danger does not mean no avalanche danger. Dangerous avalanche conditions do exist in isolated areas where the snow is thin. These are typically found on West, South and East aspects, in rocky areas or where wind has scoured the snowpack. It takes a lot of force to produce failure of the snowpack in these areas, but it fails to the ground.

Weather Forecast and Avalanche Outlook

Mostly dry and cool weather is expected for the next couple of days. Arctic air will remain in place while high pressure develops over the region. The next best chance for snow appears to be Wednesday during a transition to a Northwesterly flow aloft bringing increasing cloud cover and a bit more Pacific moisture.

Expect avalanche conditions to remain similar until we receive significant snowfall. The weak, sugary, rotten snow that formed during the cold weather in December is still there, you can find it on most aspects between 6000' and 9000' and you can never completely trust it. Although we're saying the avalanche danger is now low to moderate, it's still possible to rip out a massive slab with the right amount of force in just the right place. So what do you do? Simple! Go one at a time!

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted Friday January 30th, 2009.

January 23, Avalanche Advisory

Fri, 23 Jan 2009 00:00:00 MST
West Central Montana Avalanche Center
Avalanche Advisory
Posted Friday January 23rd, 2009 at 0630.

Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for January 23rd, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can expect avalanche conditions to remain similar unless weather conditions change significantly. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. More detailed avalanche information about the St. Regis Basin can be found on the Idaho Panhandle Forest Avalanche Center website.

This advisory is in memory of Ben Richards of Missoula, who died in an avalanche near Big Sky, MT 2 winters ago.

Weather and Snowpack Analysis

Temperatures this past week climbed into the 50's above 6000' while valley and mountain locations below about 6000' remained cool. Sunny days and cold clear nights were the rule until Thursday when a weak weather system brought cloudy skies and wind into the area.

East and South aspects warmed enough to go through several melt-freeze cycles which left a bomb-proof crust on everything. Snow conditions are firm on the other aspects and the snowpack settled further during the warmer weather. Observers are noting faceted crystals underneath the sun crust and mature depth hoar at the ground. The facets under the crust are due to a steep temperature gradient in the upper 10cm of the snowpack. This weakness will need to be watched during the next big storm.

As far as the rotten snow at the ground is concerned, we've been talking about this all winter and it just isn't going away anytime soon. The warmer weather helped glue things together now that it's cold again but those facets at the ground are pretty well insulated and remain a concern on some slopes. Areas that have shallow or thin snow cover are the most susceptible to failure at this level but it takes a lot of force. We were only able to produce failures on pockets of shallow snow (less than 100cm) on East and West aspects.

You can view 2 good examples of this on these YouTube videos:

Video 1

Video 2

Current Avalanche Danger

The avalanche danger is MODERATE above 6000' in areas where the snow is thin. These are typically found on East, South and West facing aspects. Natural avalanches are unlikely, human triggered avalanches are possible. At all other locations and elevations throughout our advisory area the avalanche danger is LOW. Natural avalanches are very unlikely, human triggered avalanches are unlikely. Low avalanche danger does not mean no avalanche danger.

Weather Forecast and Avalanche Outlook

Temperatures will continue to fall as arctic air moves into the area. Little snowfall is expected Friday with a possibility of accumulating snow Saturday and Sunday.

Expect avalanche conditions to remain similar until we receive significant snowfall. The weak, sugary, rotten snow that formed during the cold weather in December is still there, you can find it on most aspects between 6000' and 9000' and you can never completely trust it. Although we're saying the avalanche danger is now low to moderate, it's still possible to rip out a massive slab with the right amount of force in just the right place. So what do you do? Simple! Go one at a time!

If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted Monday, January 26th, 2009.

January 19, 2009 Avalanche Advisory

Mon, 19 Jan 2009 00:00:00 MST
Posted: 07:00 January 19, 2009

Good morning. This is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for January 19, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight. Today's advisory is sponsored by Becky Richards in memory of Ben Richards (pictured at the right).
The advisory area includes the Bitterroot Mountains from Lost Trail to Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Detailed avalanche information about the St. Regis Basin can be found at the Idaho Panhandle National Forest Avalanche Center .

Weather and Snowpack Analysis
It has been warm at the higher elevations. We noted temperatures of 47 degrees Fahrenheit at 8000' at 1pm on Sunday. Snow stability tests are showing stable conditions. Snotel sites around the region are indicating a settling snowpack with loss of snow depth. However, at the warmest part of the day we are seeing lots of snow on the move. At this time of the day snow is sluffing off the rocks, dropping out of the trees and moving on ski turns on the South slopes. So, for the next few days treat this as a spring snowpack. Be especially careful if riding or skiing steep rollovers or steep faces near rocks during the heat of the afternoon. There is the possibility a wet surface slab could trigger a bigger slide on the weak snow near the ground that we have been discussing for weeks.

Current Avalanche Danger
The avalanche danger is LOW Natural avalanches are very unlikely, human triggered avalanches are unlikely. Between 12noon and 3pm on slopes steeper than 30 degrees above 6000' the avalanche danger is MODERATE due to very warm temperatures at altitude. Natural avalanches are unlikely, human triggered avalanches are possible.

Weather Forecast and Avalanche Outlook
Tonight through Wednesday a persistent ridge of high pressure will maintain a stable environment across Western Montana. Low clouds will remain in the valleys. High terrain will bask in the warm sunshine. The only possibility for snow looks like Wednesday night. We should keep an eye on any crusts that are formed by the warm temperatures when it does snow, but for now we have generally stable conditions.

If you have snow observations or any snow information you'd like to share please contact us at info@missoulaavalanche.org .

The next avalanche advisory will be issued Friday January 23rd, 2009.

January 16, 2009 Avalanche Advisory

Fri, 16 Jan 2009 00:00:00 MST
West Central Montana Avalanche Center
Avalanche Advisory

Posted Friday January 16th, 2009 at 0630.

This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for January 16th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can expect avalanche conditions to remain similar unless weather conditions change significantly. The advisory area includes the Bitterroot Mountains from Lost Trail to Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. More detailed avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis

All our observers yesterday agree that we now have mostly safe conditions with a few exceptions. Dangerous conditions still exist on some terrain features especially areas where the snowpack is shallow on steep rocky terrain. It doesn't matter which way it faces the sun; some of these slopes are holding weak faceted snow on a crust near the ground which will remain for several weeks.

Temperatures were starting to climb above freezing above 7000' Thursday and the skiing and riding conditions were very good. The overall snowpack has strengthened considerably during the past 2 weeks and the weak faceted snow at the ground that had us in a fuss is showing signs of strength and bonding. I still don't trust it on some slopes, areas where the snowpack is thin in particular.

We are starting to see signs of surface hoar development, radiation re-crystallization and near surface faceting on the surface and on the zipper crust from last Sunday. This is not yet a problem but keep this bit of information tucked away for the next storm cycle.

Current Avalanche Danger

Throughout our advisory area the avalanche danger is LOW on most slopes and at all elevations. Natural avalanches are very unlikely, human triggered avalanches are unlikely. As you might expect there are some noteworthy exceptions to this welcome condition. Unstable slabs may exist on some terrain features such as wind loaded slopes steeper than 35° or areas where the snowpack is shallow with rock outcroppings where it would be easier to collapse through to the weaker facets near the ground.

On these slopes the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. Remember, we just came through a big avalanche cycle where the culprit was the faceted snow around the early December rain crust. It's still there, you can find it on most aspects between 6000' and 9000' and you can never completely trust it. Although we're saying the avalanche danger is now low to moderate, it's still possible to rip out a massive slab with the right amount of force in just the right place. So what do you do? Simple! Go one at a time!

Weather Forecast and Avalanche Outlook

A strong ridge of high pressure is settling over the Northern Rockies increasing inversions and bringing foggy, cool conditions in the valleys and warmer sunny weather in the mountains. Temperatures are expected to reach into the low 40's the next few days with little wind and clear skies.

These conditions will continue to strengthen our snowpack. Avalanche danger will increase on the Southerly aspects when the sun reaches its peak and temperatures rise above the freezing mark. Those aspects tend to be shallower and more prone to rapid warming at this time of year so pay close attention to the temperatures and avoid these warmer slopes later in the day. Wet snow avalanches involving the newest snow may step down to more deeply buried weaknesses once they start moving.

We continue to receive excellent observations from many different locations. Your snow observations are very important to us as they help us portray more accurate overall avalanche conditions in our area. Our resources are limited so information about avalanche activity or snowpack conditions you see may save a life. If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted Monday, January 19th, 2009

Avalanche Advisory for January 12, 2009

Mon, 12 Jan 2009 00:00:00 MST
posted: 06:30 January 12, 2009

Good morning. This is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for January 12, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight.
The advisory area includes the Bitterroot Mountains from Lost Trail to Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake.

Weather and Snowpack Analysis
Temperatures have moderated and we received modest amounts of snow since Friday morning. The surface instability I described Friday morning has settled out. Snow stability testing showed an improved snowpack. Snotel sites around the region are showing seasonably warm temperatures along with 1-3" of snow accumulation for the last 48 hours. This information does not indicate great powder riding or skiing, but it does indicate a welcome stability in the snowpack. On our tour into the Rattlesnakes yesterday we observed an interesting thin crust on the snow, probably due to rime, warm temperatures and high humidity. This crust is very thin, quite skiable, and should break down; but something to keep an eye on. We have seen indications and received reports that several avalanches have run to the ground on the early December crust; most of these observations have been on NW,N,NE slopes at 6000 to 7500'. Maybe everything that was going to run on the early weakness has run; but you should pay attention on steep slopes above 6000'. The weak snow is still present at the ground level but is not responding to stability tests. Ride or ski one at a time and carry the proper equipment.

Current Avalanche Danger
The avalanche danger is MODERATE above 6000' on all aspects and slopes steeper than 30°. The avalanche danger is LOW at all other locations.

Weather Forecast and Avalanche Outlook
It looks like weak high pressure will move into West Central Montana. There may be some scattered mountain showers in the mountains though Tuesday. Although these conditions favor a generally stable snowpack, there could be some pockets of snow instability. Since we have observed and seen reports of many natural avalanches you should consider the possibility that there may still be isolated slabs in steep terrain, particularly around rock outcrops or bands of rock on a slope. These types of terrain features tend to hold the weak snow at the bottom for a longer period of time.

If you have snow observations or any snow information you'd like to share please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted Friday January 16th, 2009.

For specific Lookout Pass / St. Regis Basin avalanche information visit the Idaho Panhandle National Forest Avalanche .

Education and Announcements
A Beacon Basin was installed and is operable at Lolo Pass. The Beacon Basin was installed through cooperative efforts of the West Central Montana Avalanche Foundation and the U.S. Forest Service. The training opportunity will be available when the Lolo Pass Visitors Center is open. Snowmobilers will have to walk from the parking lot to use the site. You must have a transceiver to use the site. Organized groups will need a special use permit through the Forest Service if they wish to use the site for a program.

I am presenting an avalanche awareness class for the Missoula Snowgoers Snowmobile Club at 7pm in the Montana FWP Building on Tuesday January 13 at 7pm.

Avalanche Warning January 9, 2009

Fri, 09 Jan 2009 00:00:00 MST
Posted: January 9, 2009 - 06:30

Good morning. This is Dudley Improta with the West Central Montana Avalanche Center's avalanche advisory for January 9, 2009. Today's advisory is dedicated to the memory of Ben Richards (photo at the right). This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight, although the advisory can give you valuable information for assessing snow conditions for the next 48 hours.

Steve Karkanen issued an avalanche warning on Wednesday; we are continuing that warning through today. An avalanche warning continues to be in effect for the mountains of West Central Montana above 5000'. The most recent storm has deposited warm dense snow on top of colder snow. This snow came in with high winds from the Southwest. The avalanche danger is HIGH. Natural and human triggered avalanches are likely. Unstable slabs exist on all aspects and slopes steeper than 30°. This warning includes the Bitterroot Range from Lost Trail Pass to Lookout Pass, the Rattlesnake Mountains (including Sheep Mountain in the Lower Blackfoot) and the Southern Mission and Swan Ranges near Seeley Lake. Extensive skill, experience and knowledge are necessary for safe travel in the backcountry during HIGH avalanche conditions.

Weather and Snowpack Analysis
Snow stability testing is showing very easy failures in the top layers of the snowpack. At 8000' in the Rattlesnake Mountains this surface slab is 2 feet thick! This photo shows the bed surface and depth of this slab.
.Rutschblock Test Photo
This condition is widespread in West Central Montana and is on all aspects. We didn't get rain at high elevation as predicted, we got dense heavy snow. This snow was deposited on colder snow on the surface. Reports from the Bitterroot noted 31" of new snow for the week. Along with this storm came the wind. The winds at elevation were 30mph with gusts up to 50mph. The deep instability that has been pestering us is still present but the main concern is the surface slab that could be triggered easily. This slab is present on all aspects plus Northwest, North and Northeast slopes are wind-loaded above 5000'.

Current Avalanche Danger
Throughout the advisory area and on all aspects above 5000' the avalanche danger is HIGH on all open slopes steeper than 30°. Natural and human triggered avalanches are likely.
Below 5000', the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. There is still some very weak snow near the ground at lower elevations. Any open, steep slopes are suspect. Reports from Lolo Pass (at 5600' elevation) showed stronger snow but the worrisome weak snow near the ground continues to be a concern. Observations from around the region pegged the snow/rain line at 5600'.

Weather Forecast and Avalanche Outlook
A weak high pressure with colder air is expected to move into the region and extend into the weekend. A Northwest flow aloft should produce light snow. The best chance for snow looks like Saturday afternoon and Saturday evening.
This surface instability should begin to settle out within 48 hours. The deep weak snow from the cold weather in December is still with us, but beginning to strengthen.

The next advisory will be issued January 12, 2009.
If you have any snow observations or questions please e-mail us at info@missoulaavalanche.org

For specific Lookout Pass / St. Regis Basin avalanche information visit the Idaho Panhandle National Forest at Idaho Panhandle National Forest Avalanche .

Avalanche Warning January 7, 2009

Wed, 07 Jan 2009 00:00:00 MST
Avalanche Warning
Posted Monday January 7th, 2009 at 0900.

This is Steve Karkanen at the West Central Montana Avalanche Center with a special avalanche warning for January 7th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. This avalanche warning is valid for the next 48 hours as snow levels continue to rise. The next regular avalanche advisory will be issued on Friday, January 9th.

An avalanche warning has been issued for all mountainous areas of West Central Montana including the Bitterroot Mountains from Lost Trail to Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Rain and heavy wet snow is falling onto an extremely weak snowpack. Any snow covered slope steeper than 30° that is receiving rain is now very dangerous.

Weather and Snowpack Analysis

Weak faceted snow above and below a rain crust + a dense slab of snow above the crust + light dry snow on top of the slab + another layer of wet heavy snow above the light dry snow + rain up to 6500' = widespread and potentially large destructive avalanches. Whenever rain is a factor in the snow stability equation the result of this addition to an already volatile recipe is widespread avalanche activity on all aspects and at all elevations below the snow line.

SNOTEL sites this morning are showing temperatures in the 30's and 1" to 1.5" of snow water equivalent has fallen the past few hours. Conditions are ripe for avalanches

Current Avalanche Danger

In areas where rain is occurring or expected, the avalanche danger is HIGH. Natural and human triggered avalanches are likely. Travel in avalanche terrain is not recommended without extensive avalanche assessment skills. Avoid being on or under any slope steeper than 30°

The avalanche danger is CONSIDERABLE at the higher elevations where heavy wet snow is falling onto a layer of cold, low moisture content snow that was deposited last Friday and Saturday. This inverted or upside down snow is very sensitive so slopes rated as considerable will slide into the high avalanche danger category as soon as it begins raining or while receiving a heavy load of new snow. Rain is expected to reach as high as 6500' to 7000' by Thursday.

Recently wind loaded or unanchored open slopes are dangerous. Natural avalanches are possible, human triggered avalanches probable. There are unstable slabs on many slopes just waiting for the right trigger to rip them out. Considerable avalanche danger means there are dangerous conditions out there. BE CAREFUL!

Weather Forecast and Avalanche Outlook

From the Missoula NOAA National Weather Service Forecast Office:

NORTHERN CLEARWATER MOUNTAINS-SOUTHERN CLEARWATER MOUNTAINS-BITTERROOT/SAPPHIRE MOUNTAINS-
746 PM MST TUE JAN 6 2009 /646 PM PST TUE JAN 6 2009

A WINTER STORM WARNING ABOVE 4500 FEET REMAINS IN EFFECT UNTIL 11 AM MST /10 AM PST/ WEDNESDAY. MODERATE TO HEAVY SNOWFALL IS EXPECTED OVER THE HIGHER TERRAIN THROUGH WEDNESDAY. TOTAL SNOWFALL ACCUMULATIONS OF 6 TO 10 INCHES
ARE EXPECTED...WITH LOCALLY 15 INCHES POSSIBLE. STRONG WINDS WILL RESULT IN BLOWING SNOW AND REDUCE VISIBILITY...ESPECIALLY OVER LOLO AND LOST TRAIL PASSES. SNOW LEVELS WILL RISE TO BETWEEN 5000 AND 5500 FEET BY LATE WEDNESDAY WITH SNOW CHANGING OVER TO RAIN IN THE VALLEYS. A BRIEF PERIOD OF FREEZING RAIN IS ALSO POSSIBLE.

Expect avalanche danger to remain similar or worsen until temperatures begin to drop. Slab avalanches involving the newest snow may step down to more deeply buried weaknesses once they start moving.

21 people have died in avalanches this year in the US and Canada, most of them in the past 2 weeks. Avoid travel on or under slopes steeper than 30°, never expose more than 1 person at a time to an avalanche path, carry rescue equipment and know how to use it.

SPECIAL NOTE: Many mountain ranges in Montana and Northern Idaho are not covered by avalanche advisories. Many of these areas are as popular and visited as often as the mountain ranges covered by the Avalanche Centers in this region. Backcountry recreationists seeking information about avalanche conditions in these areas should contact the local Forest Service District Office for more information. You can also interpret information provided by the Avalanche Centers, SNOTEL sites and the National Weather Service weather forecasts to determine what the snowpack conditions are like in areas that are not covered by an avalanche advisory. When avalanche danger conditions are dangerous from one avalanche advisory area to the next, chances are pretty good that mountain ranges that lie between avalanche centers have very similar conditions, particularly those ranges adjacent to covered areas. If uncertain, do call!

SPECIAL NOTE #2: Foothills areas in Western Montana are beginning to accumulate respectable snow depths. While these areas are outside of our avalanche advisory area, these areas have terrain steep enough and avalanches have happened under the right conditions. In January of 1993, a young man died in an avalanche on Mt. Jumbo within sight of East Missoula. It's worth paying attention to during unusual winter conditions and we have unusual conditions this year.

We've received many excellent observations from many different locations the past few days. Your weather and snow observations are very important to us as they help us portray more accurate overall avalanche conditions in our area. Our resources are limited so information about avalanche activity or weather conditions you see may save a life. If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org .

The next avalanche advisory will be posted Friday January 9th, 2009

January 5th, 2009 Avalanche Advisory

Mon, 05 Jan 2009 00:00:00 MST
Posted Monday January 5th, 2009 at 0630.

This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for January 5th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can expect avalanche conditions to remain similar unless weather conditions change significantly.

The advisory area includes the Bitterroot Mountains from Lost Trail to Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake.

Weather and Snowpack Analysis

Our weekend weather gave us a respite from the seemingly continual onslaught of heavy snow and high winds. Get ready, it looks like we're about to get hammered again. Several steep slopes avalanched this past week, many ran the entire distance of the path and most involved the entire snowpack at least down to the ice crust that formed in early December. Some of these avalanches were visible from the valley floor in the Bitterroot Saturday. We continue to receive great reports from many individuals nearly all of whom witnessed avalanches small and large in many areas of Western Montana up to Saturday.

Conditions improved Saturday as skies cleared and temperatures dropped into the teens giving the snow a chance to adjust. On Sunday, our observers reported that conditions are slowly starting to improve but remain dangerous on the steeper slopes. The deeply buried facets are no longer affected by cold temperatures and are showing signs of strengthening but are still a prominent weakness. It's getting more difficult to produce failures at this level but when it fails it fails with some energy. It's as if it can't wait to bust out and shed all the weight it's trying to support.

Snow is beginning to fall this morning and many areas can expect to see significant accumulation by Tuesday.

Current Avalanche Danger

The avalanche danger is CONSIDERABLE above 5000' on all aspects and slopes steeper than 30°. Recently wind loaded or unanchored open slopes remain dangerous. Natural avalanches are possible, human triggered avalanches probable. There are unstable slabs on many slopes just waiting for the right trigger to rip them out. Considerable avalanche danger means there are dangerous conditions out there. BE CAREFUL!

The avalanche danger is MODERATE at all other locations. Natural avalanches are unlikely but human triggered avalanches are possible.

Weather Forecast and Avalanche Outlook

From the Missoula NOAA National Weather Service Forecast Office:
LOWER CLARK FORK REGION-
402 AM MST MON JAN 5 2009

A WINTER STORM WARNING REMAINS IN EFFECT UNTIL 11 PM MST THIS
EVENING.

SNOWFALL WILL INCREASE AND INTENSIFY THROUGH THE MORNING AND CONTINUE THROUGH THIS EVENING. TOTAL SNOWFALL ACCUMULATIONS OF 6TO 8 INCHES IN THE VALLEYS AND 12 TO 14 INCHES IN THE HIGHER TERRAIN ARE EXPECTED BY MONDAY EVENING. LOOKOUT PASS WILL BE THE MOST IMPACTED BY THIS STORM. LOCAL GUSTY SOUTHWEST WINDS MAY CAUSE AREAS OF BLOWING AND DRIFTING SNOW.

A WINTER STORM WARNING MEANS SIGNIFICANT AMOUNTS OF SNOW... AND BLOWING SNOW ARE EXPECTED OR OCCURRING. STRONG WINDS ARE ALSO POSSIBLE. THIS WILL MAKE TRAVEL VERY HAZARDOUS OR IMPOSSIBLE.

Expect avalanche danger to worsen during this storm system. Each new load brings stability back to the tipping point. This is still a dangerous time in the mountains. Slab avalanches involving the newest snow may step down to more deeply buried weaknesses once they start moving.

21 people have died in avalanches this year in the US and Canada, most of them in the past week. Avoid travel on or under slopes steeper than 30°, never expose more than 1 person at a time to an avalanche path, carry rescue equipment and know how to use it.

SPECIAL NOTE: Many mountain ranges in Montana and Northern Idaho are not covered by avalanche advisories. Many of these areas are as popular and visited as often as the mountain ranges covered by the Avalanche Centers in this region. Backcountry recreationists seeking information about avalanche conditions in these areas should contact the local Forest Service District Office for more information. You can also interpret information provided by the Avalanche Centers, SNOTEL sites and the National Weather Service weather forecasts to determine what the snowpack conditions are like in areas that are not covered by an avalanche advisory. When avalanche danger conditions are dangerous from one avalanche advisory area to the next, chances are pretty good that mountain ranges that lie between avalanche centers have very similar conditions, particularly those ranges adjacent to covered areas. If uncertain, do call!

SPECIAL NOTE #2: Foothills areas in Western Montana are beginning to accumulate respectable snow depths. While these areas are outside of our avalanche advisory area, these areas have terrain steep enough and avalanches have happened under the right conditions. In January of 1993, a young man died in an avalanche on Mt. Jumbo within sight of East Missoula. It's worth paying attention to during unusual winter conditions and we have unusual conditions this year.

We've received many excellent observations from many different locations the past few days. Your weather and snow observations are very important to us as they help us portray more accurate overall avalanche conditions in our area. Our resources are limited so information about avalanche activity or weather conditions you see may save a life. If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted Friday January 9th, 2009

Avalanche Warning January 2, 2009

Fri, 02 Jan 2009 00:00:00 MST
Happy New Year! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for January 2nd, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can expect avalanche conditions to remain the same through the weekend.

An avalanche warning is in effect for the mountains of West Central Montana above 5000'. Heavy snow is being deposited onto an extremely weak snowpack. The avalanche danger is HIGH. Natural and human triggered avalanches are likely. Unstable slabs exist on all aspects and slopes steeper than 30° The warning area includes the Bitterroot Range from Lost Trail Pass to Lookout Pass, the Rattlesnake Mountains (including Sheep Mountain in the Lower Blackfoot) and the Southern Mission and Swan Ranges near Seeley Lake. Backcountry travel is not recommended. Avoid travel on or underneath open slopes steeper than 30°.

Expect conditions to worsen especially in areas where snow turns to rain and where strong gusty winds load already overloaded slopes. All aspects and open slopes steeper than 30° are very dangerous and are expected to remain in this condition for an extended period of time.

Weather and Snowpack Analysis

SNOTEL sites are reporting 1.5" to nearly 3.5" of SWE (snow water equivalent) in the Bitterroot Mountains and 2" SWE in the Rattlesnake and Southern Missions the past 48 hours. This translates to 15" to 30" of new snow in some locations. Temperatures are close to 30° at many mountain locations this morning.

Stability testing in all areas is showing easy failures at the level of the faceted snow above and below the rain crust that formed in early December. This is now deeply buried with a firm cohesive slab above it. We're also seeing easy failures with a wind slab that formed earlier this week during the high winds and warmer temperatures. Once this slab starts moving it quickly adds more weight to an already stressed weak layer that may fail at the ground. In other words, the mountains around Missoula are about to come unglued.

Current Avalanche Danger

Throughout the advisory area and on all aspects above 5000' the avalanche danger is HIGH on all open slopes steeper than 30°. Natural and human triggered avalanches are likely. Unstable conditions exist on any open slope especially those that have been wind loaded or where anchoring vegetation such as stumps or boulders are covered by snow. Travel in avalanche terrain is not recommended.

Below 5000', the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. The weak features we've been describing (weak faceted snow on a rain crust) have come into play in areas where the snow is deep enough to cover anchors. Unstable slabs can be found in isolated areas that have been wind loaded. These are typically on the leeward side of ridges or other terrain features, especially in open areas and can be found on all aspects.

Weather Forecast and Avalanche Outlook

A moist and strong winter storm system will continue to impact the area through Friday. Heavy snowfall and strong gusty winds will result especially across Northwest Montana and over mountain passes. Snow levels have risen to approximately 5000' over portions of West Central Montana with pockets of freezing rain resulting.

Expect this high avalanche danger to continue or worsen as we continue to receive heavy precipitation at warmer temperatures. This is a very dangerous time in the mountains. Any avalanches that release may be very large and destructive. Don't roll the dice. 19 people have died in avalanches this year in the US and Canada, most of them in the past week. Avoid travel on or under slopes steeper than 30°, never expose more than 1 person at a time to an avalanche path, carry rescue equipment and know how to use it.

SPECIAL NOTE: Many mountain ranges in Montana and Northern Idaho are not covered by avalanche advisories. Many of these areas are as popular and visited as often as the mountain ranges covered by the Avalanche Centers in this region. Backcountry recreationists seeking information about avalanche conditions in these areas should contact the local Forest Service District Office for more information. You can also interpret information provided by the Avalanche Centers, SNOTEL sites and the National Weather Service weather forecasts to determine what the snowpack conditions are like in areas that are not covered by an avalanche advisory. When avalanche danger conditions are dangerous from one avalanche advisory area to the next, chances are pretty good that mountain ranges that lie between avalanche centers have very similar conditions, particularly those ranges adjacent to covered areas.

SPECIAL NOTE #2: Foothills areas in Western Montana are beginning to accumulate respectable snow depths. While these areas are outside of our avalanche advisory area, these areas have terrain steep enough and avalanches have happened under the right conditions. In January of 1993, a young man died in an avalanche on Mt. Jumbo within sight of East Missoula. It's worth paying attention to during unusual winter conditions and we have unusual conditions this year.

Be safe, have fun and let us know what you see out there. Your weather and snow observations are very important to us. Information about avalanche activity or weather conditions seen may save a life. If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted January 5th, 2009

Avalanche Warning December 29, 2008

Mon, 29 Dec 2008 00:00:00 MST
Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for December 29th, 2008. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight.

An avalanche warning is in effect for the mountains of West Central Montana. The avalanche danger is HIGH, natural and human triggered avalanches are likely. This warning is for mountainous locations above 5000' and includes the Bitterroot Range, the Rattlesnake Mountains (including Sheep Mountain in the Lower Blackfoot) and the Southern Missions and Swan Range near Seeley Lake. Backcountry travel is not recommended. Avoid travel on or underneath open slopes steeper than 30°.

Weather and Snowpack Analysis

The faceted weak snow structure above and below the rain crust that formed in early December is now a serious problem in all areas where the snow is deep enough to cover anchors. A strong winter storm entered our area this weekend with heavy snowfall and high wind speeds. This system came in at much warmer mountain temperatures than we've seen in about 3 weeks giving us avalanche conditions that have not been seen here in years.

SNOTEL sites are reporting 1.5" to nearly 3" of SWE (snow water equivalent) in the Bitterroot Mountains and 1.5" to 2" SWE in the Rattlesnake and Southern Missions the past 48 hours. This translates to 15" to 30" of new snow in some locations. Temperatures are much warmer with this storm with temperatures approaching 30° at many mountain locations Sunday. Rain was reported to about 5500' in many areas and wind speeds were in the 80mph range on Point Six. This heavy dense snow was deposited onto very cold light snow from the past 2 weeks of cold weather and many natural avalanches ran during the day Saturday. In areas that received rain, avalanches were noted at lower elevations along road cuts or on any unanchored slope. These generally went to the ground. At higher elevations the heavy new snow has brought most slopes to the brink as the weaker faceted snow near the ground is now unable to support the weight. We've received excellent reports from backcountry travelers in the Bitterroot who witnessed large avalanches run near St Mary's Peak and Gash Point. Check out the photo of the avalanche near St Mary's that broke through the ice of a small lake in the runout zone in our photo gallery.

Stability testing in the Rattlesnake at 7600' was producing easy failures to the facets above the rain crust we've been describing. This is 20cm from the ground and depending on the location and how the wind has loaded the particular slope, the slabs that failed were anywhere from 2' to 5' deep.

One of the more disconcerting things we're seeing is the length fractures have been able to propagate. We're not talking about a few feet; we're seeing slopes fracture for hundreds of yards.

Current Avalanche Danger

On all aspects above 5000' the avalanche danger is now HIGH on all open slopes steeper than 30°. Natural and human triggered avalanches are likely. Unstable conditions exist on any open slope especially those that have been wind loaded or where anchoring vegetation such as stumps or boulders are covered by snow. Travel in avalanche terrain is not recommended.

Below 5000', the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. The weak features we've been describing (weak faceted snow on a rain crust) have come into play in areas where the snow is deep enough to cover anchors. Unstable slabs can be found in isolated areas that have been wind loaded. These are typically on the leeward side of ridges or other terrain features, especially in open areas and can be found on all aspects.

SPECIAL NOTE: The foothills around Missoula are beginning to accumulate respectable snow depths. While these areas are outside of our avalanche advisory area, there is terrain steep enough to slide and avalanches have happened under the right conditions. In January of 1993, a young man died in an avalanche on Mt. Jumbo within sight of East Missoula. It's worth paying attention to during unusual winter conditions and we have unusual conditions this year.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting that a strong Pacific Jet Stream will continue to bring moisture into Western Montana. There is potential for continued significant snowfall at the higher elevations Monday and again Wednesday. "The nature of these Pacific storm systems will likely result in more dense snow than that of a few weeks ago".

That says it all. Heavy dense snow piled onto a very weak snowpack. You bet, all this new snow is a good thing. We need it, it's coming in a way that will give us good riding and travel conditions later and it isn't 20° below zero anymore. But it is coming with a price and that price is dangerous avalanche conditions.

This is simply not a good time to travel in avalanche terrain. The snow needs time to strengthen. Avoid being on or under open slopes steeper than 30°. Does that mean you have to stay home? NO! There are plenty of places to play that are safe. There's something about making first tracks that reaches into our exploratory spirit even on the flats so use this time to explore new trails, get used to your new equipment and practice using your new (or old) avalanche transceiver. The reward for satisfying your desire for taking risks on steep ground in these conditions may end up being the worst nightmare you, your family and friends can imagine. Don't buy into the concept of it being a good thing to die while doing something you love. If you love it that much, do everything possible to make it happen again, and right now that means waiting for a safer day.

Have a super fun and safe New Year!

Your weather and snow observations are very important to us. Information about avalanche activity or weather conditions you see out there may save a life. If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted Friday January 2nd, 2009.

Avalanche Advisory for December 26, 2008

Fri, 26 Dec 2008 00:00:00 MST
West Central Montana Avalanche Advisory
Posted December 26th, 2008 at 0600.

Happy Holidays! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for December 26th, 2008. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight.

Weather and Snowpack Analysis

Observation reports are from the Bitterroot and Rattlesnake Mountains on Wednesday and we did not receive observations from the Southern Swan or Mission Mountains this week.

Remember the adage, be careful what you ask for? Well, we're getting what we've been asking for. The problem is that it's coming in a way that our current basal snowpack layers cannot support.

All locations are reporting faceted weak snow structure above and below the rain crust that formed in early December. This appears to be most pronounced in the Bitterroot Mountains at all elevations and aspects and a buried surface hoar layer is failing easily in the Rattlesnake Mountains. The Rattlesnake also has the early December rain crust and has weak faceted crystal structure, but the initial failures involve a 30cm wind slab that recently formed. These slabs could step down to more deeply buried facets near the ground. The ski patrols at both Montana Snowbowl and Lost Trail ski areas were able to initiate slab avalanches with explosives and by ski cutting steep wind loaded terrain on Wednesday.

The good news is that the new snow has been coming in gradually with a slow warm up. The weak layer near the rain crust is gaining strength over time and is adjusting quite well to each storm that slowly adds weight to it. The bad news is the cold temperatures we've experienced the past 2 weeks has allowed the weak granular sugary snow around the crust to persist so when we receive a storm that drops a lot of weight (several inches of snow or any amount of rain) it won't be able to adjust fast enough to be safe. The really bad news is that the forecast is calling for a warm up with significant snowfall and wind perhaps even rain at some mountain locations this weekend.

Current Avalanche Danger

Above 5000' on wind loaded terrain steeper than 35°, the avalanche danger is CONSIDERABLE. Natural avalanches are possible and human triggered avalanches are probable. Unstable slabs can be found in isolated areas that have been wind loaded. These are typically at the higher elevations on the leeward side of ridges or other terrain features, especially above the tree line and can be found on all aspects.

On all other aspects and elevations above 5000', the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. The weak features we've been describing (weak faceted snow on a rain crust) are coming into play in areas where the snow is deep enough to cover anchors.

Below 5000' the avalanche danger is LOW. Natural avalanches are very unlikely and human triggered avalanches are unlikely. There is very little snow at most locations below 5000'.

Weather Forecast and Avalanche Outlook

A cold front moving through the Northern Rockies has allowed snow showers to persist with light accumulations over the advisory area. Wind speed at Point Six has been in the 30mph range from the WSW for several hours now with temperatures remaining very cool in the teens and single digits. The forecast for the weekend is calling for warmer temperatures and significant mountain snowfall through Sunday. Rain is a possibility but it's a bit too early to be sure of this. Winds will be in the 20mph range from the W-SW, strong enough to move the cold light snow we've been getting onto the leeward slopes.

The avalanche danger will increase with warmer, wetter and heavier snow deposited onto the colder lighter snow that is on the ground now. This inverted or upside down snowpack condition takes time to settle out. This is a tricky time in the mountains of Western Montana so it is very important to have not only good mountain riding and travel skills, but also have good avalanche assessment skills. If in doubt about a slope, don't risk it. Save it for another day. Conditions will improve over time and we have a long winter ahead of us to enjoy. Many locations have below normal snow depths and what is there has no base. Even in areas where there is not much of an avalanche problem we're hearing of some pretty serious injuries and damage to equipment involving rocks, stumps and other debris that is covered just enough to make it look good.

Be increasing cautious in avalanche terrain. Pay particular attention to areas that have been recently wind loaded and any steep open slope where the anchors are covered. Never expose more than 1 person at a time to slopes steeper than 30°, have a transceiver, probe pole and shovel on you and know how to use them.

Your weather and snow observations are very important to us. Information about avalanche activity or weather conditions you see out there may save a life. If you have any information you'd like to share or have questions about anything related to snow safety, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted Monday, December 29th, 2008.

West Central Montana Avalanche Advisory

Mon, 22 Dec 2008 00:00:00 MST
Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for December 22nd, 2008. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight.

Weather and Snowpack Analysis

Most locations received just a few more inches of snow since Thursday and the temperatures started to moderate back into the single digits and teens at most locations. The wind Sunday turned more East-Southeasterly at 15-20 and was gusting into the 30-40mph range. This morning temperatures are close to 20 degrees at most SNOTEL sites with 2-3" of new snow overnight. More snow is in the forecast and stability conditions are getting touchier as the snow piles up and the wind blows it around.

We received a great report from the Northern Bitterroot Mountains near Hoodoo Pass where an observer's stability testing showed failures occurring at the level of the rain crust that formed on 12/6. While it took moderate force on compression tests to produce failure (CT14-20), the isolated columns slid cleanly and easily (Q1). Further North in the St. Regis Basin area, the same party noted fracture propagations, and collapse indicators on steep wind loaded slopes on mostly Southern aspects. They wisely choose to ski on less steep terrain in both locations and found decent (but thin) skiing.

In the Rattlesnake Sunday, we found highly variable (and thin) snow conditions on all aspects. A strong ESE wind was loading WNW aspects through the day and scoured the more East facing terrain. We triggered an 18-20" wind slab while crossing beneath a steep embankment on a road. While this was a small slide what was notable was the distance the fracture propagated. The fracture ran parallel to the road for approximately 450'. It failed on faceted snow that formed on a hard snow surface on what is usually a wind scoured area. Compression test scores were CTV to CTE2 with a Q1 shear plane. On slopes adjacent to this slide that turned just a few degrees to the North, our compression test scores were much higher with dirtier shear quality CTM12-24 with Q2 shear planes. This YouTube video shows a compression test on this particular aspect.

http://www.youtube.com/watch?v=AHg5CmreWYE

Current Avalanche Danger

On steep wind loaded terrain at the highest elevations (7000' - 9000') the avalanche danger is CONSIDERABLE. Natural avalanches are possible and human triggered avalanches are probable. Unstable slabs can be found in isolated areas that have been recently wind loaded. These are typically at the higher elevations on the leeward side of ridges especially above the tree line.

At other on all aspects and elevations from 7000' to 9000' the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. There are some very weak features that need close attention during the next couple of storms.

Below 5000' the avalanche danger is LOW. Natural avalanches are very unlikely and human triggered avalanches are unlikely. There is very little snow at most locations below 5000'.

Weather Forecast and Avalanche Outlook

Expect snowfall to continue through the day today as a low pressure system digs into the Northwest. This system has us under a Southwest flow which is pumping in ample moisture. The best location for snow in our area is South of I-90. A weak ridge of high pressure builds Tuesday ahead of the next storm system. The next good chance for snow appears to be coming Wednesday just in time to fill our stockings for Christmas.

Expect avalanche danger to increase as the mountains receive more snow and wind. Pay particular attention to areas that have been recently wind loaded and any steep open slope where the anchors are covered. As always, never expose more than 1 person at a time to a slope steep enough to slide, have a transceiver, probe pole and shovel on you and know how to use them.

If you have any avalanche or snowpack information you'd like to share or have questions about the upcoming season, please contact us at info@missoulaavalanche.org.

The next avalanche advisory will be posted December 26th, 2008.

Avalanche Advisory for December 19, 2008

Fri, 19 Dec 2008 00:00:00 MST
West Central Montana Avalanche Advisory
Posted December 19th, 2008 at 0600

Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the first regular avalanche advisory for the 2008-2009 season. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Weather and Snowpack Analysis

Observers at all locations in the Bitterroot and Rattlesnake Mountains report shallow unconsolidated snow cover on all aspects and elevations in the advisory area. Snow amounts range from 31" at Saddle Mountain near Lost Trail, 20" at Lolo Pass, 34" at Hoodoo and 40" at Stuart Peak. Temperatures early in the week were sub-zero and began moderating Thursday back up into the 20's. Snow was just beginning to push into the area from the West. SNOTEL sites this morning have received 3-5" of new snow overnight. Cold temperatures have allowed faceted snow to grow at the ground and around the rain crust that formed 2 weeks ago and a thin surface hoar layer developed in some areas during the clear weather last week. These features may come into play later but are not currently a problem as they are not supporting a slab and the snow is not deep enough to cover ground anchors and brush.

Current Avalanche Danger

The avalanche danger is LOW on all aspects and elevations from 5000' to 8000'. There may be isolated areas where dangerous avalanche conditions can be found on steep open terrain where ground anchors have been covered or where terrain has been wind loaded. These are typically at the higher elevations on the leeward side of ridges on North to East aspects.

Weather Forecast and Avalanche Outlook

This morning, the Missoula Office of the National Weather Service is forecasting a cold front to move through the area into Eastern Montana today. Steady snowfall will diminish this morning and transition into convective shower activity. Arctic air will spill over the continental divide later today and tonight bringing very cold wind chill temperatures into Sunday. On Sunday, a moist Pacific system moves into the Northern Rockies with potential for widespread snowfall.

Expect avalanche danger to increase this weekend as the mountains receive more snow and wind. Never expose more than 1 person at a time to a slope steep enough to slide, have a transceiver, probe pole and shovel on you and know how to use them. If you get out and see something you'd like to share with us, send us a note at info@missoulaavlanche.org . Have a safe weekend!

We are dropping our coverage of the St. Regis Basin area near Lookout Pass. We felt it was unnecessary for 2 centers to cover this area, the terrain and elevation is more similar to areas the Panhandle Avalanche Center covers in their advisory and most users are from ID and WA locations. The Idaho Panhandle NF Avalanche Center will continue to issue avalanche advisories for the St. Regis Basin. Bookmark their website at:

Idaho Panhandle Avalanche Center

If you have any avalanche or snowpack information you'd like to share or have questions about the upcoming season, please contact us at info@missoulaavlanche.org .

The next avalanche advisory will be posted December 22, 2008.

Information Update for Dec.12

Fri, 12 Dec 2008 00:00:00 MST
Early Season Avalanche Information
Posted December 12th, 2008

This is Steve Karkanen at the West Central Montana Avalanche Center with early season avalanche information and news from the avalanche center. We begin issuing regular avalanche advisories on December 19th and will update snow and weather information prior to this as conditions change. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas.

All of us at the Avalanche Center and the Bitterroot, Clearwater and Lolo National Forests express our sincere condolences to the friends and families of Lisa Jones and Steven "Max" Haldeman who died in a tragic fall near St. Mary Peak in the Bitterroot Mountains last Saturday.

It's finally starting to look like winter will arrive. NOAA Missoula Weather Service Office is forecasting a significant winter storm to begin affecting our area this weekend. A strong moist Pacific front with significant snow will move through Friday night while very cold arctic air spills over the Continental Divide from the northeast during the weekend. This collision of warm moist air from the west and very cold air from the east may result in heavy snowfall and high wind speeds. Near blizzard conditions are possible especially in the mountains and passes. The falling temperatures and high winds will also generate dangerous wind chills of as much as 30 degrees below zero in some areas Sunday night.

SNOTEL sites reported temperatures approaching 40 degrees last Saturday as a weather system moved through the area bringing rain up to 9500'. This rain left a nasty ice lens on everything as surface temperatures were in the teens and low 20's when it first arrived. This weather event was a contributing factor in last Saturday's accident. Average temperatures have been in the 20's since then and most locations picked up a few inches of snow.

We've received reports from several different areas in the Bitterroot and Southern Swan mountains this week all indicating mostly stable but shallow and funky skiing conditions. There are pockets of buried surface hoar crystals on the colder shaded aspects above 6000' and melt-freeze or rain crusts were failing with a moderate amount of force during stability testing. While these features are not currently much of a problem, they will need to be treated with suspicion once it starts snowing heavily. The primary concerns now are wind slabs on slopes steeper than 35 degrees where the anchors have been covered.

Expect avalanche danger to increase this weekend as the mountains begin to receive heavy snow and wind. Be increasingly cautious during this weekend storm. Never expose more than 1 person at a time to a slope steep enough to slide, have a transceiver, probe pole and shovel on you and know how to use them. If you get out and see something you'd like to share with us, send us a note at info@missoulaavalanche.org. Have a safe weekend!

Avalanche Advisories

We've made a few changes to our program this year. We will be issuing advisories 2 days each week, on Monday and Friday mornings starting December 19th. This is in response to backcountry users asking for updated avalanche information to cover the early part of the week. This would not be possible without the financial support from our friends group, the West Central Montana Avalanche Foundation. This organization is vital to our ability to continue to provide avalanche advisories and education in Western Montana. They are a 501 (c) 3 non-profit and you can donate directly to this good cause from this website.

We are dropping our coverage of the St. Regis Basin area near Lookout Pass. We felt it was unnecessary for 2 centers to cover this area, the terrain and elevation is more similar to areas the Panhandle Avy Center covers in their advisory and most users are from ID and WA locations. The Idaho Panhandle NF Avalanche Center will continue to issue avalanche advisories for the St. Regis Basin. Bookmark their website at:

Idaho Panhandle Avalanche Center

Beacon Basin Training Parks

Have an avalanche transceiver? Do you practice using it? Be honest... Beacon Basin training parks are a fun and user friendly way to become proficient with any type of avalanche transceiver. The Foundation has purchased 2 Beacon Basin training parks that will be operational this winter. One training park will be set up at Lolo Pass and another at Montana Snowbowl. Users will be required to check out the control unit from the Visitor Center staff at Lolo Pass and from the ski patrol at Snowbowl. There is no cost to use these excellent training tools.

Check out this article about Beacon Basin Training Parks:

www.ikar-cisa.org/ikar-cisa/documents/2007/2005-TC-15-Beacon-basin-Tracker.pdf

If you have any avalanche or snowpack information you'd like to share or have questions about the upcoming season, please contact us at info@missoulaavalanche.org.

Regular avalanche advisories will be posted starting December 19, 2008.

Early Season Avalanche Information and News

Tue, 25 Nov 2008 00:00:00 MST
Early Season Avalanche Information
Posted November 25, 2008

Happy Thanksgiving! This is Steve Karkanen at the West Central Montana Avalanche Center with early season avalanche information and news from the avalanche center. We begin issuing regular avalanche advisories on December 19th and will update snow and weather information prior to this as conditions change.

SNOTEL sites in the Bitterroot and the Rattlesnake are showing around 12" of snow on the ground w/ Saddle Mountain SNOTEL (near Lost Trail Pass) reporting about 15". The high elevations near Seeley Lake also have about 12". There is no snow below 6000' in most areas and not much anticipated in the next few days. Not to worry. It will snow, it always does. In the meantime, make sure all your winter backcountry equipment is in good working condition, put new batteries in your transceiver and start preparing to recognize where and when you are in a situation where an avalanche could happen. The best way to do this is to take a class. We have several scheduled this winter and many more to come. Check out our events and education page for upcoming classes.

Avalanche Advisories

We've made a few changes to our program this year. We will be issuing advisories 2 days each week, on Monday and Friday mornings starting December 19th. This is in response to backcountry users asking for updated avalanche information to cover the early part of the week. This would not be possible without the financial support from our friends group, the West Central Montana Avalanche Foundation. This organization is vital to our ability to continue to provide avalanche advisories and education in Western Montana. They are a 501 (c) 3 non-profit and you can donate directly to this good cause from this website.

We are dropping our coverage of the St. Regis Basin area near Lookout Pass. We felt it was unnecessary for 2 centers to cover this area, the terrain and elevation is more similar to areas the Panhandle Avy Center covers in their advisory and most users are from ID and WA locations. The Idaho Panhandle NF Avalanche Center will continue to issue avalanche advisories for the St. Regis Basin. Bookmark their website at:

http://www.fs.fed.us/ipnf/visit/conditions/backcountry/bcupdate.html

Beacon Basin Training Parks

Have an avalanche transceiver? Do you practice using it? Be honest... Beacon Basin training parks are a fun and user friendly way to become proficient with any type of avalanche transceiver. The Foundation has purchased 2 Beacon Basin training parks that will be operational this winter. One training park will be set up at Lolo Pass and another at Montana Snowbowl. Users will be required to check out the control unit from the Visitor Center staff at Lolo Pass and from the ski patrol at Snowbowl. There is no cost to use these excellent training tools.

Check out this article about Beacon Basin Training Parks:

http://www.ikar-cisa.org/ikar-cisa/documents/2007/2005-TC-15-Beacon-basin-Tracker.pdf

If you have any avalanche or snowpack information you'd like to share or have questions about the upcoming season, please contact us at info@missoulaavalanche.org.

Have a great holiday!

Regular avalanche advisories will be posted starting December 19, 2008.

Early (way early) Season News

Tue, 26 Aug 2008 00:00:00 MST

Good afternoon. This is Dudley Improta with the West Central Montana Avalanche Center. It's August, but ski equipment guides are already on the shelves. The very good news is the Lolo National Forest has agreed to add another advisory each week to the Center. This means an updated advisory will come out on Friday morning and on Monday morning for the 08/09 season. A lot of credit has to go to folks with the West Central Montana Avalanche Foundation who worked so hard to raise money to support this extra advisory. Also businesses who supported the website and bought ads and the donors deserve credit as well. Now the Foundation will be raising funds to continue the advisories, the educational offerings and build avalanche beacon parks in the area. Tentatively the first park will go on Forest Service land at Lolo Pass. Look for information on the Burning Dog Pray for Snow Festival at Big Sky Brewery the evening of October 17. But, it 's ok to start praying before the Festival.

Late Season Information / Update

Fri, 11 Apr 2008 00:00:00 MST
Good Morning! This is Dudley Improta with the West Central Montana Avalanche Center. We ended formal advisories last weekend. However, we have received some reports from the backcountry and we are due for a significant weather change this weekend; and this is not the spring snowpack we have been used to for a long while.

This update does not apply to operating ski areas. If you are climbing, skiing or riding at a closed-for-the-season ski area, you should treat it as the backcountry.

Weather Forecast:
Snow showers are possible through Friday morning with possible accumulation above 5000 feet. A high-pressure ridge is building to move in Friday evening, which is predicted to produce warming under mainly clear skies. Temperatures at 8000 feet could reach 57 to 67 degrees F. on Sunday. We have not seen temperatures at elevation like this for some time.

Visit
http://www.wrh.noaa.gov/mso/
for the most recent weather information for West Central Montana.

Hazard Update
There are layers in the pack that are still failing cleanly, although with a lot of force. There are some big cornices out there on exposed leeward ridges, as well. This morning Snotel sites in the region are showing 2 to 3 inches of new snow along the Idaho border and 4 to 5 inches in the Rattlesnakes. Pay particular attention and use caution on all steep slopes during the heat of the day this weekend. The southerly aspects have some weaknesses in the upper snowpack and we have observed weak layers on northerly aspects as deep as three feet from the surface. There was a reported skier -triggered slab avalanche on a southerly aspect during the heat of the day on April 4 in the Rattlesnakes. Temperatures were recorded above 40 degrees F. on April 4. Temperatures are expected to be quite a bit higher than that this weekend.

This update expires at midnight Friday April 11, 2008.

Thanks for all the observations and support this year!

April 4, 2008 Avalanche Advisory

Fri, 04 Apr 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted April 4, 2008 at 0700

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for April 4-6, 2008. The avalanche danger rating expires at midnight April 4th. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas. John Lehrman at Backcountry Focus sponsors today's advisory.

Weather and Snowpack Analysis

Most mountain locations received up to a foot of new snow this past week. Temperatures remained cool until Thursday when skies cleared and gave us one of the nicer days we've seen this winter. Temperatures shot up into the 40's at many locations but dropped below freezing as soon as the sun went over the ridge. Shaded slopes retained the finest snow while everything on the bottom half of the compass (east to west) started the slow trip to the Pacific. Temperatures this morning are in the low 20's at 8000' and I would expect it to warm up again today if the sun stays out. A strong storm system is expected to make its way into the area later this afternoon bringing significant precipitation by Saturday especially in the Bitterroot Mountains. Snow levels will drop to around 4500' as the storm passes.

Observers reported mostly stable conditions at all locations with some small point release slides observed involving the snow surface on steep sun exposed terrain. Southern aspects have the weakest snow right now as crusts that formed a few weeks ago fail cleanly under moderate force about 18" deep. These slopes are going to be heinous skiing anyway and I would avoid them during the heat of the day.

Today's Avalanche Danger

Above 5000' on slopes steeper than 35 degrees, the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. There may be unstable slabs on steep terrain.

Below 5000' and on all other terrain less steep than 35 degrees, the avalanche danger is LOW. Natural avalanches are very unlikely, human triggered avalanches are unlikely. There may be isolated pockets of unstable snow at the lower elevations even during periods of LOW avalanche danger.

During periods of rapid warming or rain, the avalanche danger will quickly increase to CONSIDERABLE on all slopes steeper than 35 degrees. Natural avalanches are possible, human triggered avalanches probable.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting that a strong storm system will enter the area late Friday. Temperatures and snow levels will begin dropping as this system makes its way into Montana. The Bitterroot Mountains have the best chance for snowfall accumulation possibly heavy amounts in some locations.

This is the final avalanche advisory for this season. Mountain locations continue to accumulate snow and April can be a big snow month in the Northern Rockies. We have not seen any significant warm up or rain above 6000' all winter. Once we have temperatures that remain above freezing for several hours or if we get any rain, I would expect to see widespread avalanche activity involving some of the now deeply buried weak layers we've been keeping an eye on this winter.

If you are seeking further backcountry travel information please contact the local Forest Service Ranger District Office in the area where you wish to recreate or call us at 406-329-3752.

March 28 Avalanche Advisory

Fri, 28 Mar 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted March 28th at 0700

Greetings backcountry sliders and riders! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for March 28th - 30th, 2008. The avalanche danger rating expires at midnight March 28th. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Weather and Snowpack Analysis

We are well beyond the first day of spring and nearly into April but you wouldn't know it if you have been in the mountains this week. Temperatures were in the teens, the new snow was light and a delight to ski and the winds above 8000' were blasting away at the exposed ridges and mountain tops just like we've seen all winter long. So is it Spring? You bet, but there is no sign of it in the mountains above 5000'. We did have a day or two early in the week when the sun brought temperatures above freezing and warmed high elevation slopes enough to leave a nasty breakable crust on all but the most shaded aspects.

Observers Thursday reported cold temps, a foot or more of new snow in the past few days and high winds at all locations in the Bitterroot and Rattlesnake mountains. The wind was the predominant weather feature as it was easily transporting the new snow onto leeward terrain. South to West aspects were getting scoured hard by the wind but we were finding pockets of sensitive snow wherever it could accumulate. Wind slabs were forming along the high ridges and open terrain and will be sensitive for a few days. East to North aspects have the best snow and where not influenced by wind loading, mostly stable conditions.

The Lolo Pass and Rattlesnake areas picked up the most snow and observers here and elsewhere were seeing low stability test scores associated with the new snow on a hard surface. Steep wind loaded terrain is the most sensitive. The variability in skiing and stability conditions was huge yesterday so it will pay to have a high level of awareness this weekend.

We did not receive a report from the Seeley Lake area this week. The North Fork Jocko SNOTEL reports 10" new snow in the past 48 hours so conditions in the Southern Missions and Southern Swans will be similar to those seen in the Rattlesnake.

Today's Avalanche Danger

Above 5000' on all wind loaded slopes steeper than 35 degrees, the avalanche danger is CONSIDERABLE. Natural avalanches are possible, human triggered avalanches are probable. Unstable slabs exist on steep wind loaded terrain. This condition will be found on the leeward side of ridges or open terrain where high winds are present. Any East to North facing aspect above the tree line will be heavily loaded just below the ridge top.

On all other slopes steeper than 35 degrees, the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. There may be unstable slabs on steep terrain. West to Southeast aspects where wind has filled in or cross loaded steep terrain are of particular concern. These slopes have a prominent sun crust that formed during the warm sunny weather last weekend and will fail easily with enough snow (10" or more) and a trigger.

Below 5000' and on all other terrain less steep than 35 degrees, the avalanche danger is LOW. Natural avalanches are very unlikely, human triggered avalanches are unlikely. There may be isolated pockets of unstable snow at the lower elevations even during periods of LOW avalanche danger.

Weather Forecast and Avalanche Outlook

Another strong low pressure system will move into the area Friday with moderate to heavy snow accumulations Friday night and Saturday. 10"- 20" of snow with 13-18 mph South to West winds is possible above 6000' by Sunday.

If these conditions materialize expect the avalanche danger to worsen especially on steep wind loaded terrain. The cooler temperatures are allowing weaknesses associated with buried sun crusts and small grained facets to persist for a much longer period than normal for this time of year.

The final formal advisory for the 2007-2008 season will be posted on April 4th, 2008.

If you are seeking further backcountry travel information please contact the local Forest Service Ranger District Office in the area where you wish to recreate or call us at 406-329-3752.

March 21, 2008 Avalanche Advisory

Fri, 21 Mar 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted March 21st at 0700

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for March 21st - 23rd, 2008. The avalanche danger rating expires at midnight March 21st. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Weather and Snowpack Analysis

Mountain locations above 5000' continue to receive bursts of accumulating snowfall. While these short-lived impulses of moisture are not big precipitation producers they have slowly added more snow to an already above normal snowpack. The snow we've been seeing is of a higher density and quickly settles once on the ground. This type of snowfall accumulation bodes well for stability as the snowpack has plenty of time to adjust to the new load and gain strength. All observers are reporting mostly stable conditions with high stability test scores and good skiing and riding conditions. 8000' winds have been moving snow at the ridge tops so any leeward aspects must be treated with caution as wind slabs were forming on these slopes.

Today's Avalanche Danger

Above 5000' on slopes steeper than 35 degrees the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible.

On all other slopes the avalanche danger is LOW. Natural avalanches are very unlikely, human triggered avalanches are unlikely. Low to moderate avalanche danger never means NO avalanche danger.

At this time of year the danger of wet snow avalanches may quickly increase to CONSIDERABLE when sun exposed slopes warm above the freezing point or whenever we receive rain at the higher elevations.

Weather Forecast and Avalanche Outlook

A Snow Advisory is in effect until 3PM for the Bitterroot and Sapphire mountains. A Pacific weather system will move into Northwest Montana Friday bringing a few inches of snow to the mountains above 2500'. High pressure will build in behind this system Friday night through Saturday night. Another system will move into the area on Sunday

Cooler weather and little snowfall will keep the avalanche danger at LOW to MODERATE conditions until the next significant snowfall or warm up.

While this is probably the most stable condition we've seen this winter, it is no time to let your guard down. Never expose more than 1 person at a time on a slope steep enough to slide, always carry and know how to use an avalanche transceiver, probe poles and shovel.

We received news of an avalanche fatality that occurred on March 16 in a remote area North of Orofino, ID. The preliminary information we have is that a group of friends were snowmobiling near Sheep Mountain when 3 riders were caught in a slide on an old harvest unit. 1 person was killed and 1 injured. Our thoughts are with the family and friends of the person who died in this avalanche.

The next avalanche advisory will be posted on March 28th, 2008.

If you are seeking further backcountry travel information please contact the local Forest Service Ranger District Office in the area where you wish to recreate or call us at 406-329-3752.

March 14 Avalanche Advisory

Fri, 14 Mar 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted March 14th at 0700

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for March 14th - 16th, 2008. The avalanche danger rating expires at midnight March 14th. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas. This weeks advisory is sponsored by Backcountryfocus.com.

Weather and Snowpack Analysis

Moderate temperatures and little snow accumulation helped stabilize the weakness we described last week that involved 18"-24" of new snow on a hard snow surface. We received reports of avalanches that occurred last Friday and Saturday that failed at this level. There were no reported injuries but at least one close call in the Rattlesnake.

Warm sunny weather Sunday and Monday left a nasty melt freeze crust on all but the most sheltered North aspects. This zipper crust will be the next feature to pay attention to if we receive several inches of snow during the next storm. It failed easily on South and east aspects during our stability tests. In the Southern Bitterroot near Lost Trail Pass, last weeks snow buried surface hoar in many locations and that feature is failing cleanly about 12" deep into the snowpack. It has gained strength the past few days but remains a concern on the steeper slopes. Observers in the Lolo Pass and Lookout Pass areas reported a much stronger overall condition than a week ago but remind us that there are still slabs out there on steep or wind loaded terrain that could be triggered by a skier or snowmobile. The overall condition has improved with the warmer weather and lack of precipitation.

Today's Avalanche Danger

Above 6000' in the Bitterroot Mountains from Lookout Pass South to Lost Trail Pass, the Rattlesnake Mountains North of Missoula, and the Southern Swan and Mission Mountains near Seeley Lake, the avalanche danger is MODERATE on slopes steeper than 35 degrees. Natural avalanches are unlikely, human triggered avalanches are possible.

On all other slopes the avalanche danger is LOW. Natural avalanches are very unlikely, human triggered avalanches are unlikely. Low to moderate avalanche danger never means NO avalanche danger.

At this time of year the danger of wet snow avalanches may quickly increase to CONSIDERABLE when sun exposed slopes warm above the freezing point or whenever we receive rain at the higher elevations.

Weather Forecast and Avalanche Outlook

The Missoula NOAA Weather Service is forecasting scattered to occasionally widespread snow showers through the weekend period. Snowfall accumulations are not expected to be significant for the next few days. Do return to the backcountry weather forecast each afternoon for an update on weather forecasts as NOAA Missoula Weather Service updates the backcountry weather every day by 3 PM.

Cooler weather and little snowfall will keep the avalanche danger at LOW to MODERATE conditions until the next significant snowfall or warm up.

The next avalanche advisory will be posted on March 21st, 2008.

If you are seeking further backcountry travel information please contact the local Forest Service Ranger District Office in the area where you wish to recreate or call us at 406-329-3752.

March 7, 2008 Avalanche Advisory

Fri, 07 Mar 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted March 7th at 0600

Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for March 7th - 9th, 2008. The avalanche danger rating expires at midnight March 7th. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Weather and Snowpack Analysis

West Central Montana mountain locations received an average of 2.25" of snow water equivalent since last Friday (2/29). North Fork Jocko, Stuart Peak and Twin Lakes SNOTEL stations picked up about 25" of new snow most of which came in hard on Tuesday and early Wednesday. Other Bitterroot SNOTEL sites received 12" of snow at Lost Trail and Lolo passes to closer to 18"-20" at Hoodoo and Lookout passes. This new snow is very dense or heavier and wetter than earlier storms we've seen this winter and was deposited onto a firm snow surface that formed during warm sunny weather 2 weeks ago. There are also many areas where surface hoar crystals formed on this snow surface which was subsequently buried by a few inches of snow. We have also seen graupel deposited onto this old snow surface during last weekend's snow.

On Thursday, temperatures moderated, the sky cleared and the recent storm snow began to settle out. We received several excellent reports this week from skiers in many locations in the Bitterroot who noted weakness associated with either buried surface hoar or faceted snow on or just under the late February crusts. Many of these sites were getting very low stability scores prior to the snow that came in on the 4th and many of these backcountry skiers and riders wisely backed away from tempting powder shots. These reports are significant in that many of these locations now have a much deeper slab. A good example of what we're seeing in the Rattlesnake and hearing about in other locations can be seen on YouTube here:

http://www.youtube.com/watch?v=Ocs8vr1E5Y8

This particular video shows how easily and quickly a small slab of dense snow can pull someone off balance and send them tumbling down the hill. RB2 Q1.

http://www.youtube.com/watch?v=poXyuArKnAM

The Rattlesnake snowfall was a big surprise for everyone Wednesday. As in most other locations, this new snow has not yet had the time needed to adjust and bond to the old snow surface. Another day or two should be enough time needed to stabilize the condition we saw Thursday but clear sky conditions and warm air temperatures will increase the danger of wet snow avalanches on any steep, sun-exposed terrain.

Today's Avalanche Danger

In the Rattlesnake Mountains North of Missoula, the Southern Mission Mountains and the Southern Swan Range near Seeley Lake, MT, the avalanche danger is CONSIDERABLE above 6000' on all North to Southeast aspects steeper than 35 degrees or on any wind loaded or cross loaded slope steeper than 35 degrees. On other aspects above 6000' the avalanche danger is MODERATE. Below 6000' the avalanche danger is LOW.

In the Bitterroot Mountains from Lost Trail Pass North to Lookout Pass the avalanche danger is CONSIDERABLE above 5000' on all North to Southeast aspects steeper than 35 degrees or on any wind loaded or cross loaded slope steeper than 35 degrees. On other aspects above 5000' the avalanche danger is MODERATE. Below 5000' the avalanche danger is LOW.

CONSIDERABLE avalanche danger means natural avalanches are possible and human triggered avalanches are probable. Unstable slabs are probable on steep terrain so be increasingly cautious on steeper terrain.

MODERATE avalanche danger means natural avalanches are unlikely and human triggered avalanches are possible. Unstable slabs are possible on steep terrain.

Weather Forecast and Avalanche Outlook

A weak upper level shortwave weather system Friday will be followed by a stronger Pacific system Friday night and Saturday. This second system is expected to bring only light snow accumulation through Saturday evening. A ridge of high pressure will then build for the remainder of the weekend bringing warming and dry conditions through Monday when another Pacific system enters the area with warm moist air increasing the chance for rain in the valleys and snow showers in the mountains.

As mentioned above, the current instability will need a bit more time to settle out and glue itself to the hard surfaces it came in on. Moderate temperatures will certainly help speed this process but if we see temperatures quickly rise above freezing, wet snow avalanche danger will also quickly rise.

The next avalanche advisory will be posted on March 14th, 2008. If you are seeking further information please contact the local Forest Service Ranger District Office in the area where you wish to recreate or call us at 406-329-3752.

February 29 Avalanche Advisory

Fri, 29 Feb 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted February 29th at 0700

This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for February 29- March 2nd, 2008. The avalanche danger rating expires at midnight February 29. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas. This advisory is sponsored by Becky Richards and Moonlight Basin Ski Resort in memory of Ben Richards who died in an avalanche accident on Yellow Mountain near Big Sky on March 3, 2007. Ben is sorely missed by his family and friends here and in Big Sky.

Weather and Snowpack Analysis

Mountain temperatures have been swinging through periods of thaw and freezing with just a touch of moisture earlier in the week. The Twin Lakes SNOTEL reported a high of 50 and a low of 23 on Wednesday. At other sites high temperatures were in the high 30's / low 40's but all nighttime temperatures dropped back into the 20's. SNOTEL stations reported close to an inch of snow water equivalent with little or no gain in depth. Some areas are finding surface hoar and faceted crystals under a thin crust that may become reactive if they receive a big load of snow. This condition seems to be most pronounced in the area around Lolo Pass. Observers here were getting easy failures 20cm deep into the snow with obvious surface hoar at this level. This will be a layer of concern during and after the next big storm. At all other locations observers were reporting a very solid snowpack and were not getting any appreciable stability test results. The report from the Lost Trail Pass area indicated that it would take a bulldozer to get it to fail.

Today's Avalanche Danger

With cooler temperatures at the higher elevations the snow is locked into a solid state this morning. At all mountain locations of West Central Montana the avalanche danger is LOW, natural avalanches are very unlikely and human triggered avalanches are unlikely. As temperatures rise above freezing or whenever it rains, the avalanche danger will quickly rise to a CONSIDERABLE condition where natural avalanches are possible and human triggered avalanches probable.

Weather Forecast and Avalanche Outlook

NOAA Missoula Office is forecasting a ridge of high pressure to persist through Friday afternoon when a strong front and upper trough will move into the area late Friday. Because of the warmer than normal air mass, snow levels will start out fairly high well into Saturday when cooler air aloft moves in. Snow is expected to reach the valley floors Saturday and the Bitterroot Mountain passes are expected to receive 5"-6" of snowfall.
We've had several days now that have helped to further stabilize the overall snowpack. There are some notable exceptions to this as always. Many areas have buried surface hoar and radiation recrystalized snow (faceted snow crystals) that is not currently a problem but may be the next time we see appreciable snowfall. Be mindful of this and treat any wind loaded slope with a good deal of suspicion until you have ruled out any threat from these upper level weaknesses. During warm sunny days, travel early then move onto the shaded aspects later in the day. If it rains, it's probably time to go home anyway. Rain will be a big problem for us especially above 6000'.

Be safe and keep sending those great reports! They really do help. Send observations to info@missoulaavalanche.org.

The next avalanche advisory will be posted on March 7th, 2008.

February 22 Avalanche Advisory

Fri, 22 Feb 2008 00:00:00 MST
February 22 Avalanche Advisory
Posted: February 22, 2008 at 0700
Weekend Avalanche Advisory

Good Morning! This is Dudley Improta with the West Central Montana Avalanche Center's weekend avalanche advisory for February 22-24, 2008. The avalanche danger rating expires at midnight February 22. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas. This weekend's advisory is dedicated in memory of Ben Richards of Missoula, who died in an avalanche near Big Sky in March of 2007.

Weather and Snowpack Analysis
The snow stopped falling in West Central Montana by Sunday Feb. 17. Snotel sites in West Central Montana are recording significant settling, anywhere from 6 to 10 inches. This kind of settlement in the snowpack generally indicates stability. Weather telemetry also recorded temperatures well above freezing at higher elevations during the day. Two things to think about are rapid warming during the day and the production of surface hoar during the clear nights. The snow may become unstable around rock ridges or outcrops during periods of rapid warming, particularly on East aspects during the morning and West and South aspects in the afternoon. Surface hoar is being noted in the Bitterroots. This surface hoar may produce an unstable layer if we get snow on top of it. This will be something to look for on North and Northeast slopes. The sun will have destroyed most of the surface hoar on other aspects. All observers are reporting generally stable conditions but the snow in the Rattlesnakes and the Lolo Pass area have some weakness in the upper pack. The Rattlesnake Mountains had a fair amount of wind the last two weeks that was not recorded in other areas. The wind caused layers about 35 cm into the snowpack in the Rattlesnakes that warrant attention for the next few days. A layer similar to the Rattlesnake layer is also present in the snowpack around the Lolo Pass area.

Today's Avalanche Danger

Above 6000' in all advisory area locations, the avalanche danger is MODERATE on all slopes 35 degrees and steeper, particularly in the heat of the afternoon. Natural avalanches are unlikely and human triggered avalanches are possible. Use caution in steeper terrain. Below 6000' the avalanche danger is LOW. Normal caution is advised. Even during periods of LOW hazard isolated areas of instability may exist.

Weather Forecast and Avalanche Outlook:
A ridge of high pressure will continue into Friday evening. A weak system will move through the region Friday night into Saturday. The higher terrain may get some accumulating snow. Snow amounts are not expected to be over 2 inches and winds are predicted to be light. Another system is expected Sunday with a possibility of more snow and winds to 10 mph. Avalanche hazard may increase during the warmest periods of the day and the surface hoar noted in the Bitterroots may get buried by the snow predicted for Saturday and Sunday.

If you want to send us an observation or report an avalanche, go to missoulaavalanche.org and click on "submit an observation".

Many thanks to the University of Montana, Montana Fish, Wildlife & Parks and the Missoula Office of the National Weather Service for their support of this website.

Steve Karkanen will post the next avalanche advisory on February 29, 2008.

February 15 Avalanche Advisory

Fri, 15 Feb 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted February 15th at 0600

This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for the Presidents Day Weekend, 2008. The avalanche danger rating expires at midnight February 15th. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas. Thanks to John Lehrman of Backcountryfocus.com for the help in the Southern Bitterroot this week.

Weather and Snowpack Analysis

Warm temperatures, heavy snowfall and rain were the big weather events last weekend. Most areas received rain up to about 5000' Sunday then temperatures dropped with a fast moving system that also dropped several inches of snow. This newest snow is bonding well in most locations but as noted in the Rattlesnake, some wind loaded pockets were failing on density changes. This will continue to gain strength over time. You can see an example of this on YouTube:

http://www.youtube.com/watch?v=aomoWcaLwqM

There is evidence of avalanche activity that occurred last Sunday in many areas of the Bitterroot Mountains. Many of these avalanches ran on the MLK layer (a thin layer of faceted snow and surface hoar now 4' deep) that continues to rear its ugly head whenever we get a big dump or major change in temperatures. This layer can still be found in most locations above 5000' but has strengthened to the point where it is not much of a concern under the current weather and snow conditions. However, when and where we get it to fail, it fails cleanly with a lot of energy. It's something to think about when we start to warm up or get rain above 5000'.

Today's Avalanche Danger

Above 5000' in all advisory area locations, the avalanche danger is MODERATE. Natural avalanches are unlikely. Human triggered avalanches are possible.

Below 5000' the avalanche danger is LOW. Natural avalanches are very unlikely and human triggered avalanches are unlikely. Low avalanche danger does not mean there is no avalanche danger.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting high pressure to build today then a disturbance will brush through Friday night and Saturday with only minor amounts of precipitation. Another stronger ridge of high pressure begins building Sunday into early next week. Mountain temperatures are expected to warm as an inversion sets up and intensifies in the western valleys.

Expect conditions to continue to improve with the current forecast until temperatures rise above the freezing point or whenever the higher elevations receive rain or heavy snowfall. The weakness that formed after the MLK holiday is now deeply buried and takes a lot of force to produce failures. But we still find that it is unable to support a rapid load or quick change in conditions in many areas. Avalanches that ran to the river on Highway 12 earlier this week remind us that the right combination of new snow load, warm temperatures or rain can produce large destructive avalanches in areas that seem stable.

Dudley Improta will post the next avalanche advisory on February 22, 2008.

Avalanche Advisory Feb. 8, 2008

Fri, 08 Feb 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted February 8 at 0700

Good Morning! This is Dudley Improta with the West Central Montana Avalanche Center's weekend avalanche advisory for February 8-10, 2008. The avalanche danger rating expires at midnight February 8. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.
We would like to thank and acknowledge Sue and Rick Neff, local veteran skiers, for their generous donation to missoulaavalanche.org.

Weather and Snowpack Analysis

The snow in West Central Montana had started to settle but we were hit with a series of storms in the latter part of the week. It is worth noting that Idaho Department of Transportation personnel observed very deep crowns from natural avalanches along the Idaho side of Lolo Pass earlier in the week. They were there to use guns to control the snow along highway 12. It appeared these avalanches ran on the crust that formed on MLK weekend. That crust and weak snow has persisted, but it is taking some force to get it to fail in stability tests. It is buried 2 to 3 feet below the surface but still breaking cleanly. Our concern this weekend will be with the new snow from the storms that started Wednesday night.
Weather telemetry sites around the region are registering 14 to 16 inches of new snow accompanied by steady winds at 30 mph. Winds are predominately out of the West and Southwest. Observers reported up to 50cm (20 inches) of ski penetration while breaking trail. Even though observers did not report the cracking and settling of the snow like last week, they all felt the new snow with the unrelenting winds deserve attention.
You can view the snow layers on youtube:
http://www.youtube.com/watch?v=2bq62pOftjs

http://www.youtube.com/watch?v= MsJOKBpppns

Today's Avalanche Danger

Above 5000' in all advisory area locations, the avalanche danger is CONSIDERABLE on all slopes steeper than 30 degrees. Natural avalanches are possible and human triggered avalanches are probable. Increasing caution on steeper terrain is advised. Below 5000' the avalanche danger is MODERATE on slopes steeper than 35 degrees and LOW at all other locations.
THE EXCEPTION TO THIS FORECAST IS THE LOOKOUT PASS AND ST. REGIS BASIN regions within the advisory area. Above 5000' in the Lookout Pass area on all slopes steeper than 30 degrees the avalanche danger is HIGH. Natural and human triggered avalanches are likely. Travel in avalanche terrain is not recommended.

Weather Forecast and Avalanche Outlook:

A winter storm warning for West Central Montana remains in effect until 5am MST Saturday. Areas of heavy snow are predicted to continue accompanied by 25mph winds. Both Lolo Pass and Lookout Pass will be among the areas impacted. A milder westerly flow is expected to develop by Sunday with still some chances of snow. Remember most natural avalanche activity occurs during and immediately after storms and wind is a major architect of avalanches.
.

If you want to send us an observation or report an avalanche, go to missoulaavalanche.org and click on "submit an observation".

The next avalanche advisory will be posted on February 16, 2008

Avalanche Warning Feb. 1, 2008

Fri, 01 Feb 2008 00:00:00 MST
February 1 Avalanche Advisory
Posted: February 1, 2008
Weekend Avalanche Advisory
Posted February 1 at 0700

Good Morning! This is Dudley Improta with the West Central Montana Avalanche Center's weekend avalanche advisory for February 1-3, 2008. The avalanche danger rating expires at midnight February 1. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

AVALANCHE WARNING

An Avalanche warning is in effect for the mountains of West Central Montana. Above 5000' on all slopes steeper than 30 degrees, the avalanche danger is HIGH. Natural and human triggered avalanches are likely. In the past 24 hours, heavy dense snow has been deposited onto a weak snowpack structure in the following areas: the Bitterroot Mountains from Lost Trail Pass North to Lookout Pass, the Rattlesnake Mountains North of Missoula (including Sheep Mountain/Wisherd Ridge), and the Southern Swan and Southern Mission Mountains near Seeley Lake.

Weather and Snowpack Analysis

The last week in January brought another healthy dose of snow along with winds. Avalanches closed I-90 near Lookout Pass last Sunday and on the same day bombs from the Snow Bowl Patrol produced sizeable slab avalanches that had loaded on west aspects. The temperatures that had been warm because of inversions again returned to single digit numbers at higher elevations. These temperatures helped produce weak snow that is now buried within the snowpack.

SNOTEL sites around the region are registering 14 to 33 inches of new snow as of Thursday evening. Winds, predominately out of the Southwest, have accompanied these storms. The anemometer atop Point Six in the Rattlesnakes registered winds in the 20 to 30 mph range with gusts into the 40 mph range. Lookout Pass was closed to emergency travel only on Thursday because of blizzard conditions.
Observers reported recent natural avalanche activity, cracking in the snow surface and settling. They also noted that snow was falling at higher elevations at more than an inch an hour.

You can check out the layers we are concerned with on You Tube:

http://www.youtube.com/watch?v=LGTQ8ksKsbE

http://www.youtube.com/watch?v=n5aQvPI6tl

Today's Avalanche Danger

Above 5000' in all advisory area locations, the avalanche danger is HIGH on all slopes steeper than 30 degrees. Natural and human triggered avalanches are likely. Travel in avalanche terrain is not recommended. Below 5000' the avalanche danger is MODERATE on slopes steeper than 35 degrees and LOW at all other locations.

Weather Forecast and Avalanche Outlook

Another round of significant snowfall is expected Friday as a weather disturbance moves in from the west. This system should exit the area late Friday afternoon. An unsettled weather pattern will continue through the weekend, this may produce more snow. Expect the unstable snow conditions to continue during periods of heavy snowfall and high winds.

If you want to send us an observation or report an avalanche, go to missoulaavalanche.org and click on "submit an observation".

The next avalanche advisory will be posted on February 8, 2008.

January 25 Avalanche Advisory

Fri, 25 Jan 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted January 25th at 0700

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for January 25th-27th, 2008. The avalanche danger rating expires at midnight January 25th. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Weather and Snowpack Analysis

Last weekend brought another foot of snow to most locations then temperatures plummeted into the negative numbers. This cold blast was short lived as mountain temperatures have moderated the past couple of days. Temperatures this morning are much warmer at the higher elevations due to the inversion with most SNOTEL sites showing temperatures around 15 degrees. 8000' winds at Point Six are 20mph from the W-SW. The cold clear conditions this week are giving us abundant surface hoar formation in many areas.

Observers report mostly stable and challenging skiing conditions. The wind hammered all the high elevation locations and no aspect was spared. Some locations have thin wind slabs that will need to be treated with caution but overall conditions are significantly more stable than what we've been seeing this season. The surface hoar seen on our tours is spread around on multiple aspects but the wind has blown it off the more open exposed terrain. This will be the next weakness to be concerned with once this is buried. Observers in the Southern Bitterroot reported small wind slabs failing on hard old snow surfaces on North aspects along with some shooting cracks in localized areas.

Today's Avalanche Danger

Above 5000' in all advisory area locations, the avalanche danger is MODERATE. Natural avalanches are unlikely. Human triggered avalanches are possible. Below 5000' the avalanche danger is LOW. Natural avalanches are very unlikely and human triggered avalanches are unlikely. Low avalanche danger does not mean there is no avalanche danger.

Weather Forecast and Avalanche Outlook

A weak weather disturbance will bring increased cloud cover and light snow showers to the area Friday. A more active upper level pattern will bring a chance of heavier snowfall for the higher terrain Saturday night into Sunday. Winds aloft will increase bringing gusty winds to the mountain peaks. A winter storm watch has been issued for the Northern Clearwater Mountains for Saturday afternoon into Sunday. Moderate to heavy snowfall could impact the area as low pressure passes through the area.

Expect snowpack stability conditions to worsen during periods of heavy snowfall and high wind. We now have abundant surface hoar in widespread areas of West Central Montana. This is not a problem today but once it's buried, it has a nasty reputation for setting up the perfect conditions for an avalanche cycle.

We've been getting awesome reports from many different areas recently. These reports really do help us piece together an advisory that covers a large area. If you want to send us an observation or report an avalanche, contact us by sending an email to info@missoulaavalanche.org.

The next avalanche advisory will be posted on February 1, 2008.

January 18 Avalanche Advisory

Fri, 18 Jan 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted January 18th at 0700

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for January 18th -20th, 2008. The avalanche danger rating expires at midnight January 18th. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Weather and Snowpack Analysis

We continued to receive short bursts of snow the past few days. All mountain SNOTEL sites report 1.2" of Snow Water Equivalent (SWE) or about 12" of new snow. Twin Lakes and North Fork Jocko each received 2.4" so there are a few places that picked up even more snow. High elevation winds pounded the area last Friday and temperatures began dropping into the single digits. Yesterday temperatures moderated but are expected to begin dropping into the sub-zero zone sometime this weekend. The mountains North of Missoula picked up an additional 6" overnight. The main weather concern has been the wind and the ability to form tricky slabs on leeward terrain.

Observers report mostly stable conditions and very good skiing and riding conditions at all locations this week. Everyone reported significant snow transport and wind slab formation at the higher elevation sites or any location exposed to wind. Overall stability continues to improve with a couple of notable exceptions. These wind slabs formed over a layer of cold, low density snow and were showing moderately easy failures when force was applied. This condition can be found in nearly all locations above 6000'. A good video clip of this slab can be seen here:

http://www.youtube.com/watch?v=c0obgp1oChQ

We received a report of a skier triggering this wind slab on Sheep Mountain last Sunday and going for a 400' ride in Bowl 3. He was not injured and very lucky as this small slide strained him through small trees.

The other concern is the now deeply buried faceted snow that formed in early December. Although this feature is taking a lot of force to fail, it remains a concern because when it fails, it does so cleanly with energy and will be destructive. This is the layer that failed in the tragic accident in Canyon Creek near Whitefish where 2 people died last Sunday. During periods of heavy loading, this weak layer may become reactive.

Today's Avalanche Danger

Above 5000' in all advisory area locations, the avalanche danger is MODERATE. Natural avalanches are unlikely. Human triggered avalanches are possible. Above 6000' there may be pockets where the avalanche danger is CONSIDERABLE on recently wind loaded terrain steeper than 35 degrees. Natural avalanches are possible and human triggered avalanches probable. The most likely place to find these pockets of unstable snow is on East to North aspects or wherever the wind has recently deposited new snow.

Below 5000' the avalanche danger is LOW. Natural avalanches are very unlikely and human triggered avalanches are unlikely. Low avalanche danger does not mean there is no avalanche danger.

Weather Forecast and Avalanche Outlook

A strong short wave will move into the Northern Rockies tonight bringing an increased chance for moisture and accumulating snowfall. 6000'-8000' winds will again be a factor as this system passes. Temperatures are expected to drop into the single digits and lower as cold arctic air moves in from the Northeast and imbeds itself in the Western valleys.

Expect snowpack stability conditions to worsen during periods of heavy snowfall and high wind. Pay close attention to areas recently wind loaded. Avoid rocky areas or pockets where the snowpack is thin. These are likely places where it would be possible to initiate a fracture propagation involving the deepest weak layer. This is not the year to completely trust what you see out there. The avalanche near Whitefish earlier this week is an unfortunate reminder of that.

We've been getting awesome reports from many different areas recently. These reports really do help us piece together an advisory that covers a large area. If you want to send us an observation or report an avalanche, contact us by sending an email to info@missoulaavalanche.org.

The next avalanche advisory will be posted on January 25th, 2008.

January 11 Avalanche Advisory

Fri, 11 Jan 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted January 11th at 0700

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for January 11th -13th, 2008. The avalanche danger rating expires at midnight January 11th. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Weather and Snowpack Analysis

The mountains of West Central Montana received another shot of moisture this past week with most Bitterroot Mountain Range SNOTEL sites picking up 2.2" to 2.6" of snow water equivalent (SWE) since last Friday. This translates to 20" to 25" of new snow. Saddle Mountain SNOTEL and Stuart SNOTEL picked up 1.8" and 1.6" or about 15" of new snow. All this snow was spread out over the course of the past 7 days so there has been plenty of time for the snowpack to adjust to this new weight. 8000' wind speeds have been in the 30 to 35mph range for most of the week. Last Friday high winds from the East then South scoured many sites and left a very hard surface near ridgelines.

Observers report mostly stable conditions and very good skiing and riding conditions at all locations except the very Southern Bitterroot near Lost Trail Pass. Skiing conditions were fine however stability testing produced easy failure at the level of the deeply buried faceted layer associated with the early December crust. While this may be an isolated weak spot, it is worth noting as a potential problem. Observers here felt the avalanche danger is CONSIDERABLE on steeper wind loaded slopes. In the Rattlesnake, observers noted fracture propagations and easy failures on recently formed wind slabs. These were not very big slabs but a lot of snow has been moved onto leeward terrain in the past few hours. Expect to find sensitive and deeper wind slabs near the ridgelines. The wind this morning is out of the W-SW averaging 30mph at 8000'.

Today's Avalanche Danger

Above 5000' in all advisory area locations, the avalanche danger is MODERATE. Natural avalanches are unlikely. Human triggered avalanches are possible. Above 6000' there may be pockets where the avalanche danger is CONSIDERABLE on recently wind loaded terrain steeper than 35 degrees. Natural avalanches are possible and human triggered avalanches probable. The most likely place to find these pockets of unstable snow is on East to North aspects or wherever the wind has recently deposited snow on the hard surface created during the big wind last week.

Below 5000' the avalanche danger is LOW. Natural avalanches are very unlikely and human triggered avalanches are unlikely. Low avalanche danger does not mean there is no avalanche danger. Snow is as variable as the mountains we like to play on and you can almost always find a pocket of snow that will avalanche given enough weight or shock applied to it.

Weather Forecast and Avalanche Outlook

A Heavy Snow Warning is in effect for the Bitterroot-Sapphire Mountains, the Clearwater Mountains and the Lower Clark Fork region until 3PM Friday. Expect several inches of new snow by tonight with another system expected to move into the area Saturday.

Expect snowpack stability conditions to worsen during periods of heavy snowfall and high wind. Overall snowpack conditions continue to strengthen and the faceted weak layer we've been describing for a while now is deeply buried and able to take a lot of weight and force before it fails. The main avalanche concern this weekend will be how well new snow bonds to the snow surface and how heavily the wind loads leeward terrain.

The next avalanche advisory will be posted on January 18th, 2008.

January 4 Avalanche Advisory

Fri, 04 Jan 2008 00:00:00 MST
Weekend Avalanche Advisory
Posted January 4th at 0600

This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for January 4th -6th, 2008. The avalanche danger rating expires at midnight January 4th. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Weather and Snowpack Analysis

The New Year ushered in a bit of a break from the seemingly non-stop snow and wind all areas within the advisory area have seen the past several days. We received reports of large natural avalanches in the Bitterroot near Lolo Peak, and in the Southern Swan and Southern Mission Mountains that released on or before December 31st during the last of the storm cycle that blasted through the area prior to New Years Day. Most locations received close to 20" of new snow since last Friday with high W-SW winds associated with the storm passage.

Since New Years Day, temperatures and wind speeds moderated and allowed the snowpack to settle out and gain strength. While most observation sites are showing much improved stability, the weak layers we have been describing for several weeks have persisted and are now deeply buried*. This is somewhat disconcerting as it takes a lot of force or weight to trigger failure at this level but when it fails it fails with a vengeance, as if it were spring-loaded. Although it takes a lot of force or weight to initiate failure, this type of slab can be very destructive. With this in mind, the best way to mitigate the hazard is to expose only 1 person or 1 sled on any steep open slope.

*(see a good representative photo and snow pit profile of this in our photo gallery at http://www.flickr.com/photos/missoulaavalanche)

All observers are reporting very similar conditions from Lost Trail Pass to Lookout Pass in the Bitterroot, the Rattlesnake and Southern Swan and Mission Mountains. Of course the depths vary greatly but the layer of weak faceted snow is a widespread condition. Some locations also have buried surface hoar at varying depths but the predominant concern is with the faceted snow that formed early in December after the first avalanche cycle and warm up that occurred. This layer can be found between 50 and 80cm from the ground at most high elevation sites. It can be found on all aspects and seems to be more sensitive on shallower snowpack.

Today's Avalanche Danger

Above 5000' in all advisory area locations, the avalanche danger is MODERATE. Natural avalanches are unlikely. Human triggered avalanches are possible. Be aware that there may be pockets where the avalanche danger is CONSIDERABLE especially on recently wind loaded terrain steeper than 35 degrees. Natural avalanches are possible and human triggered avalanches probable. The most likely place to find these pockets of unstable snow is on East to North aspects.

Below 5000' the avalanche danger is LOW. Natural avalanches are very unlikely and human triggered avalanches are unlikely. Low avalanche danger does not mean there is no avalanche danger. Snow is as variable as the mountains we like to play on and you can almost always find a pocket of snow that will avalanche given enough weight or shock applied to it.

Weather Forecast and Avalanche Outlook

An upper level trough will move into our area Friday bringing snow accumulation and gusty winds to the higher terrain. This storm starts out warm then gradually cools. This is just what we want for the New Year, more snow and no rain.

Expect snowpack stability conditions to gradually strengthen until significant precipitation returns to the area.

As mentioned earlier, stability conditions have greatly improved over the entire area. The main concern will be how well new snow will bond to the current snowpack and just how much weight or shock the weak layer can take. We have seen 2 active avalanche cycles, the latest over the holidays, all associated with facets that formed on the old snow surface after the warm weather during the first week in December. This most recent period of avalanche activity was notable in that the size and depth of the reported avalanches is of a nature that we have not seen here for several years. We've enjoyed very stable conditions in Western Montana for the past 6 years and many of us have grown accustomed to this. Don't let your guard down. It may take a lot to get a failure at this deeper instability but the consequences would be devastating. If you must ski or ride on avalanche terrain remember; 1 at a time, watch your partner from a safe area, always wear and carry rescue equipment (transceiver, probe and shovel) and have a plan if something bad happens. Your companions need to rescue you, nobody else can.

The next avalanche advisory will be posted on January 11th, 2008.

New Years Eve Avalanche Warning

Mon, 31 Dec 2007 00:00:00 MST
This is Steve Karkanen at the West Central Montana Avalanche Center with an avalanche conditions update for New Years Eve and New Years Day. The avalanche danger rating expires at midnight on December 31, 2007. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Avalanche Warning

An Avalanche Warning is in effect for the mountains of West Central Montana above 6000'. This warning includes the Bitterroot Range from Lost Trail Pass North to Lookout Pass, the Rattlesnake Mountains (including Sheep Mountain) and the Southern Swan and Mission Mountains near Seeley Lake. The avalanche danger is HIGH: Natural and human triggered avalanches are likely. In the past 48 hours, heavy snow has been deposited onto a weak snowpack structure. All SNOTEL sites are showing 1" to 2" of SWE or more than 12"-20" of new snow since Friday morning. This is over 40" in many areas in the past few days. 8000' wind speeds have been in the 30-45 MPH range from the W-SW for the duration of this current storm system. These winds have loaded E_NE aspects heavily and they are especially sensitive right now. Other aspects may have been cross-loaded. This warning expires at midnight on New Years Eve and you can expect the avalanche danger to remain HIGH into New Years Day. Avoid traveling on or beneath slopes steeper than 30 degrees, carry an avalanche transceiver, probe pole and shovel and never expose more than 1 person at a time to avalanche terrain.

Weather and Snowpack Analysis (from 12/28)

We continue to receive a steady dose of moisture at the higher elevations in West Central Montana. Most SNOTEL sites accumulated around 2" of Snow Water equivalent (SWE) which translates to about 20" of new snow. Wind speeds remain in the 30's at 8000' so this new snow is getting moved around. The snowpack has had a few days to settle out and gain strength but the cooler temperatures are allowing weak layers to persist in many areas. The major weakness is associated with a buried surface hoar layer and faceted snow that formed after the warmer temperatures of early December.

On Thursday, observers were reporting an overall strengthening of the snowpack but the described instabilities are persisting in all areas. Stability testing produces fast clean shear plane failures with a moderate amount of force. In some areas of the Bitterroot (Lolo Pass and Gash Peak) Rutschblock scores are very low and failing at the buried surface hoar layer (RB2 Q1). This is pretty sensitive so the recommendation to riders and skiers is to play on the lower angle slopes for a few more days.

We received several reports of both natural and human triggered avalanches that occurred last weekend in the Rattlesnake, on Wisherd Ridge, in the Crystal Theater near Lolo Pass and many naturals in all locations. No one was injured in any of these incidents and in all cases the individuals felt good about stability after digging a pit and performing stability testing.

Today's Avalanche Danger (updated 12/30/07)

At all locations above 6000' in the Bitterroot Range from Lost Trail Pass to Lookout Pass, the Rattlesnake Mountains (including Sheep Mountain) and the Southern Missions and Swan Range near Seeley Lake, the avalanche danger is HIGH on open terrain steeper than 30 degrees. Wind loaded areas are especially sensitive now. Natural and human triggered avalanches are likely.

At other mountainous locations throughout the advisory area the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible.

At elevations below 5000' the avalanche danger is LOW.

Weather Forecast and Avalanche Outlook

SNOW AND GUSTY WINDS ARE EXPECTED THROUGH TONIGHT AS BRISK MOIST NORTHWEST UPPER LEVEL FLOW CONTINUES OVER THE NORTHERN ROCKIES. CONDITIONS WILL BECOME DRIER BEGINNING MONDAY AS HIGH PRESSURE BUILDS OVER THE AREA. SOUTHERLY FLOW BEGINS TO PUMP WARMER AIR OVER THE REGION BY MONDAY AFTERNOON...BUILDING VALLEY INVERSIONS INITIALLY...THEN BRINGING WARMER TEMPERATURES TO BOTH MOUNTAINS AND VALLEYS BY WEDNESDAY. (From NOAA Missoula Office National Wx Service).

We are now at the tail end of this current storm system. While most avalanches happen during and immediately after a storm, many avalanche accidents happen on the first sunny day after a storm. It's looking like we may have a bit of a reprieve in the stormy weather for a day or two and the lure of this very deep snow can easily overpower our better judgment.

This is a tricky snowpack right now. Pit observations aren't always showing any weakness yet avalanches are being triggered just a few yards from a pit site. The deeper snowpack near ridgelines and in wind loaded areas appear more stable than shallower snow just down slope. All our observers are reporting a strengthening condition but are still getting high quality shears when enough force is applied. Keep in mind there is a weak layer out there that is persistent and just waiting for the right trigger. Expect avalanche conditions to worsen if the anticipated weather system drops heavy snowfall amounts at the higher elevations. Be especially mindful during periods of heavy snowfall and wind.

The next avalanche advisory will be posted on January 4th, 2007.

Avalanche Advisory for December 28-30, 2007

Fri, 28 Dec 2007 00:00:00 MST
Weekend Avalanche Advisory
Posted December 28, 2007 at 0700

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for December 28-30, 2007. The avalanche danger rating expires at midnight on December 28, 2007. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Weather and Snowpack Analysis

We continue to receive a steady dose of moisture at the higher elevations in West Central Montana. Most SNOTEL sites accumulated around 2" of Snow Water equivalent (SWE) which translates to about 20" of new snow. Wind speeds remain in the 30's at 8000' so this new snow is getting moved around. The snowpack has had a few days to settle out and gain strength but the cooler temperatures are allowing weak layers to persist in many areas. The major weakness is associated with a buried surface hoar layer and faceted snow that formed after the warmer temperatures of early December.

Observers are reporting an overall strengthening of the snowpack but the described instabilities are persisting in all areas. Stability testing produces fast clean shear plane failures with a moderate amount of force. In some areas of the Bitterroot (Lolo Pass and Gash Peak) Rutschblock scores are very low and failing at the buried surface hoar layer (RB2 Q1). This is pretty sensitive so the recommendation to riders and skiers is to play on the lower angle slopes for a few more days.

We received several reports of both natural and human triggered avalanches that occurred last weekend in the Rattlesnake, on Wisherd Ridge, in the Crystal Theater near Lolo Pass and many naturals in all locations. No one was injured in any of these incidents and in all cases the individuals felt good about stability after digging a pit and performing stability testing.

Today's Avalanche Danger

At all locations above 6000' in the Bitterroot Range from Lost Trail Pass to Lookout Pass, the Rattlesnake Mountains and the Southern Missions and Swan Range near Seeley Lake, the avalanche danger is CONSIDERABLE on open terrain steeper than 35 degrees. Wind loaded areas will be especially sensitive during new snowfall. Natural avalanches are possible, human triggered avalanches are probable.

At other mountainous locations throughout the advisory area the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible.

At elevations below 5000' the avalanche danger is LOW.

Weather Forecast and Avalanche Outlook

An active weather pattern is setting up for the weekend. A strong Pacific system will move into the area late tonight and remain through the weekend. This system has the potential to bring heavy snowfall amounts to the higher mountains.

This is a tricky snowpack right now. Pit observations aren't always showing any weakness yet avalanches are being triggered just a few yards from a pit site. The deeper snowpack near ridgelines and in wind loaded areas appear more stable than shallower snow just down slope. All our observers are reporting a strengthening condition but are still getting high quality shears when enough force is applied. Keep in mind there is a weak layer out there that is persistent and just waiting for the right trigger. Expect avalanche conditions to worsen if the anticipated weather system drops heavy snowfall amounts at the higher elevations. Be especially mindful during periods of heavy snowfall and wind.

The next avalanche advisory will be posted on January 4th, 2007.

Avalanche Warning Update

Sun, 23 Dec 2007 00:00:00 MST
Posted 1:15pm Sunday Dec. 23
Avalanche Warning Update

Good afternoon, this is Dudley Improta with the West Central Montana Avalanche Center. The conditions that Steve described below in the Friday advisory still exist. We have confirmed two skier triggered avalanches in the mountains north and east of Missoula that occured Saturday Dec. 22. The avalanches were big enough to bury or injure someone. We don't have detailed information on either of the incidents reported to us at this time. Cold weather has allowed the weak layers to persist in the snowpack.
The avalanche danger is HIGH in the Bitterroot Range from West of Hamilton North to Lookout Pass and in the Rattlesnake Mountains (including Sheep Mountain). Natural and human triggered avalanches are likely.
This danger rating expires tonight (Sunday Dec. 23) but
these conditions may take several days to stabilize.
Steve will post the regular advisory Friday morning Dec. 28. Have a safe and happy holiday!

Weekend Avalanche Advisory
Posted December 21, 2007 at 0700

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for December 21-23, 2007. The avalanche danger rating expires at midnight on December 21, 2007. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

Avalanche Warning

An Avalanche Warning has been issued for the mountains of West Central Montana. This warning includes the Bitterroot Range from West of Hamilton North to Lookout Pass and the Rattlesnake Mountains (including Sheep Mountain). The avalanche danger is HIGH: Natural and human triggered avalanches are likely. In the past 48 hours, heavy snow has been deposited onto a weak snowpack structure. Wind loaded slopes are especially sensitive right now. Natural and human triggered avalanches have been reported to the Center and we expect this condition to continue for the next several hours. This warning expires at midnight Friday night and you can expect the avalanche danger to remain CONSIDERABLE for a few more days. Avoid traveling on or beneath slopes steeper than 30 degrees, carry an avalanche transceiver, probe pole and shovel and never expose more than 1 person at a time to avalanche terrain.

Weather and Snowpack Analysis

Most of the advisory area received abundant snowfall and high winds this past week with the Northern Bitterroot receiving the heaviest amount of moisture. Snow water equivalent at Lookout Pass SNOTEL was 3.9", Hoodoo at 4.8", Lolo Pass 3.2", Twin Lakes 2.6" and Saddle Mountain at .9" SWE. This translates to well over 2.5 to 3.5 feet of new snow in the Northern Mountains. This heavy snow was deposited on a weak layer of facets or a hard crust that formed in late November and was exhibiting all the classic signs of instability Thursday. We received several reports of natural and human triggered avalanches in the Bitterroot and Rattlesnake and widespread collapsing and whoomping of the snowpack in all locations except the very Southern portion of the Bitterroot near Lost Trail Pass and in the areas near Seeley Lake where the snowpack remains in a mostly stable condition.

As noted from SNOTEL data, snowfall amounts taper off as you go south and east. Most of our observers were reporting easy failures at the interface of the older snow surface and the accumulation from the past 2 weeks, now more than 2' deep. At the higher and more open sites, there is buried surface hoar at this interface and it is very sensitive to weight. This condition appears to be widespread above 7000'. Observation sites near Lookout Pass, Lolo Pass and in the Rattlesnake were noting easy failures at this level (about mid-pack). We have not seen conditions like this for quite some time now so prudence dictates that we go with an avalanche warning for these areas for the next few hours.

In the very Southern Bitterroot Mountains near Lost Trail Pass and in the Southern Swans near Seeley Lake, these areas did not receive the heavy snow and observers here indicate mostly stable conditions.

Today's Avalanche Danger

The avalanche danger is HIGH in the Bitterroot Range from West of Hamilton North to Lookout Pass and in the Rattlesnake Mountains (including Sheep Mountain). Natural and human triggered avalanches are likely. Avoid wind loaded slopes steeper than 30 degrees.

Near Lost Trail Pass the avalanche danger is MODERATE increasing to CONSIDERABLE as you travel north into areas that received heavy snowfall above 6500' this week.

The avalanche danger is MODERATE in the Southern Swan Mountains near Seeley Lake.

At elevations below 5000' the avalanche danger is LOW.

LOW: Natural avalanches very unlikely. Human triggered avalanches unlikely.

MODERATE: Natural avalanches unlikely. Human triggered avalanches possible.

CONSIDERABLE: Natural avalanches possible. Human triggered avalanches probable.

HIGH: Natural and human triggered avalanches likely.

EXTREME: Widespread natural or human triggered avalanches are certain.

Weather Forecast and Avalanche Outlook

The weather system that brought the snow is exiting the area today. There is enough moisture in this unstable air mass to allow a few more inches of snow to get squeezed out by this evening when a ridge of high pressure begins building. By Saturday evening this short lived break will give way to more mountain showers and high winds for the next several days.

Snow stability conditions are pretty sketchy right now but will improve with time. The transition from an unstable condition to a stable condition won't happen overnight and you must consider that we now have a persistent weak layer (buried surface hoar) in many areas. We are at the tail end of an active avalanche cycle so use extra caution when recreating in the backcountry this weekend. This is not a good time to jump into a big open steep slope. Collapse noise and recent avalanche activity are huge clues we to often ignore. The snow was screaming instability at us yesterday so give it a chance to adjust. We received an interesting report from skiers near Downing Mountain (west of Hamilton) who triggered 2 slab avalanches after digging a pit and finding stable conditions. They triggered the slides on wind loaded terrain some distance from their pit. Good travel protocol and communication between partners made the difference for this group. This is a good example of just how variable snow conditions can be and to be careful when making decisions based on one set of data.

The next avalanche advisory will be posted on December 28, 2007.

Avalanche Advisory for December 14, 2007

Fri, 14 Dec 2007 00:00:00 MST
Weekend Avalanche Advisory
Posted December 14, 2007 at 0700

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with this weekend's avalanche advisory. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight on December 14, 2007.

Today's advisory is dedicated in memory of Ben Richards of Missoula, who died in an avalanche near Big Sky last March. Enjoy your turns Ben, you've earned them.

Weather and Snowpack Analysis

Since our last update on December 7th, West Central Montana stayed cool with temperatures dropping into the single digits early in the week and only a few inches of snowfall on Monday and early Thursday. Our observation sites picked up anywhere from 6-10 inches of new snow in the past 7 days. The most important weather factor this week has been the wind. Wind speeds at 8000' have been in the steady 20-30 mph range all week coming from the East last Friday and Saturday then turning more westerly on Saturday (12/8). These high winds moved a lot of snow onto the leeward slopes. Most locations have low total snow depths but the higher elevation lee ridgeline slopes have as much as 200cm (80") in isolated areas. It is currently snowing at most mountain locations with wind speeds into the 30 mph range at 8000'.

Southern Bitterroot Mountains from Lost Trail Pass to Lolo Peak:
We received many excellent reports from the Southern Bitterroot where skiers have been keeping an eye on faceted snow near the ground. The area experienced an active avalanche cycle on December 3 when more than 2' of heavy dense snow was deposited onto a thin, weak snowpack. Many of our observers did find faceted snow near the ground but this layer has gained quite a bit of strength over the past 2 weeks. It is still something to be aware of in areas where the snow is shallow.

Lolo Pass Area:
The area around Lolo Pass doesn't yet have enough snow to cover anchors and where the snow was deep enough stability tests indicated a mostly stable condition. Higher elevation sites will be similar to the Southern Bitterroot.

Northern Bitterroot near Lookout Pass:
In the St. Regis Basin observers found faceted snow near the ground and under a rain crust at mid-pack that formed during a rain event last week. Stability testing in 73cm of total snow produced failures at 47cm with moderate force. Rutschblock testing on a 35 degree slope was producing quality 2 failures at the rain crust when skis were weighted (RB3, Q2). While not a big slab, this will need to be watched carefully as the area receives more snow. The overall snowpack here is thin and colder temperatures will allow this weakness to persist. Wind loaded slopes will be the most sensitive with new snow and wind.

Rattlesnake Mountains:
The most sensitive feature in the Rattlesnake was the interface of the newest snow on a firm wind slab with surface hoar crystals. This is of low consequence until we receive several inches of new snow. Faceted snow near the ground has gained strength. Stability testing indicates a mostly stable condition with the newest snow sloughing easily on the older hard surface and the weaker faceted snow failing after application of moderate to hard force. RB5/Q2-3, CTM17/Q2, ECTN all at 20cm. Watch out for rocks.

Seeley Lake Area-Southern Swan and Mission Mountains:
Observers at Seeley Lake had difficulty getting into the higher terrain and reported low snowpack depths. The snow at 6500' was 70cm (28") with new snow on a hard rain crust at 60cm. The snow underlying this crust is faceted to the oldest snow on the ground and it was easy to break through it. The colder temperatures are allowing this weakness to persist. Again, not much snow to be a problem yet at the lower elevations but this could be a problem layer if we receive heavy snow.

Today's Avalanche Danger

In the Rattlesnake, Southern Mission, Southern Swan and Bitterroot Mountains above 7000', the avalanche danger is MODERATE on open wind-loaded East to North aspects steeper than 35 degrees. At all other elevations and aspects the avalanche danger is LOW. Many locations have a thin snowpack where vegetation and other natural anchors have yet to be covered. It is possible to find pockets of instability in areas where the snow is thin and where recently wind loaded

LOW: Natural avalanches very unlikely. Human triggered avalanches unlikely.
MODERATE: Natural avalanches unlikely. Human triggered avalanches possible.
CONSIDERABLE: Natural avalanches possible. Human triggered avalanches probable.
HIGH: Natural and human triggered avalanches likely.
EXTREME: Widespread natural or human triggered avalanches are certain.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service has issued a winter storm watch for Friday night through Saturday afternoon. A Pacific storm system will bring a chance of significant snow and high winds across the area before a weak ridge of high pressure builds over the Northern Rockies on Sunday. Models indicate that another strong system will move into the area Monday. Expect an active weather pattern for the next few days.

With that in mind, expect avalanche conditions to worsen during periods of heavy snow and wind. Be aware of the weaknesses described above, especially places where surface hoar was buried and areas where the snow remains shallow and weak near the ground.

We need more snow so we'll take it any way we can get it. If you want to report on conditions or see avalanche activity please send an email to info@missoulaavalanche.org. We really like those reports! Thanks!

The next avalanche advisory will be posted on December 21, 2007.

Early Season Update

Fri, 07 Dec 2007 00:00:00 MST
Good morning, this is Dudley Improta with the West Central Montana Avalanche Center and an early season avalanche information update for Dec. 7, 2007. Regular weekend avalanche advisories will begin on Dec. 14.

West Central Montana received some significant snow earlier this week. The Idaho / Montana border picked up more than two feet of snow by Monday evening, Dec. 3. Colder temperatures prior to that week helped form faceted snow at the ground. So we have some heavier dense snow sitting on top of that faceted snow.

We have had several reports this week of the snowpack collapsing and some natural avalanche activity on steep slopes (40 degrees). While most of the activity reported happened earlier in the week you should pay attention if plan to recreate in the high country. Some of the faceted snow on the ground may persist for some time.

If you hear collapsing noises or observe old avalanches or cracks in the snow it may behoove you to avoid steep slopes for the time being. Open north, east or northeast slopes and bowls would be most prone to any slab avalanche activity.

The Missoula office of the National Weather Service expects a cold airmass to push into West Central Montana this weekend. It is not expected to produce much snow but it is expected to cause gusty winds near ridgetops and a downward trend in temperatures. Enough wind could move snow to leeward slopes and increase the load. Colder temperatures can delay any settling or strengthening of the snowpack.

It's still early in the season so pay attention to rocks, downfall and debris as well as the avalanche potential.

Local ski areas are opening, some of them on a limited basis. This update does not apply to operating ski areas. If you climb at an unopened ski area you should ask first and treat it as if it were the backcountry.

If you are out and see avalanche activity or just want to report some information about your observations, please send us a note from our website. We have scheduled several avalanche awareness sessions this winter and are available to give avalanche safety presentations to groups or businesses in Western Montana. Many of these sessions are posted on our Education and Events page. We are also scheduling avalanche awareness classes for grades 5-12. Call us at 406-329-3752 for further information.

Early Season Update for December 1, 2007

Fri, 30 Nov 2007 00:00:00 MST
Hi! This is Steve Karkanen at the West Central Montana Avalanche Center with an early season avalanche information update for November 30, 2007.

West Central Montana has been under the influence of a fairly wet but very cool air mass that continues to produce snow showers over the area. Average temperatures have been in the low 20's at most mountain locations and the SNOTEL sites have picked up a few more inches of snow since Thanksgiving.

While most mountain locations don't yet have enough snow to be a problem, there are places where you can easily trigger an early season avalanche. These places tend to be leeward open slopes steeper than 30 degrees where wind blown snow is deep enough to cover anchors. 8000' wind speeds have been in the 30 mph+ range on several occasions this past week which is certain to load the leeward slopes. Even a small avalanche on a small slope can have severe consequences so travel with a partner, never expose more than 1 person at a time in avalanche terrain and be prepared to take care of yourself if things don't go as planned. We've been getting some reports from backcountry skiers who are noticing faceted snow at the ground and surface hoar crystals in some areas of the Southern Bitterroot. These spotty weaknesses may be a problem if the snow is deep enough, the slope steep enough and if someone blindly jumps onto one of these weaker areas.

The Missoula Office of the National Weather Service is forecasting the possibility of significant mountain snow by Saturday night as the upper level flow transitions back to a more southwesterly pattern. This may allow warm pacific moisture to stream over the colder air at the surface causing significant snow. Weather models suggest continued moisture and warming temperatures through midweek. Significant snowfall at warmer temperatures may cause an unstable situation (heavier wetter snow deposited on drier lighter snow) until the snowpack has a chance to adjust to the new load. Pay close attention to changes in the weather during the 1st few days of December.

We begin issuing regular weekend advisories on December 14th. If you are out and see avalanche activity or just want to send us some information about what you see out there, please send us a note from our website. We are working with limited information right now so any observations we receive from the field are very helpful. Local ski areas are in the early stages of opening and may or may not allow you uphill travel on their slopes. The best policy is to ask and treat any unopened ski area as if it were the backcountry.

We have scheduled several avalanche awareness sessions this winter and are available to give avalanche safety presentations to groups or businesses in Western Montana. Many of these sessions are posted on our Education and Events page. We are also scheduling avalanche awareness classes for grades 5-12. Call us at 406-329-3752 for further information.