Observation Date: 01/15/2012

Route/Location:
We toured from Bryan Lake up the Middle Fork of Bear Creek to the south ridge of Sky Pilot (In the Bitterroots, West of Victor), and from there the summit. Returned to Bryan Lake by a similar route. The top 800′ on Sky Pilot were wind scoured down to the talus. We also did some laps on west facing slopes directly above Bryan Lake.

Weather:
The weather alternated between strong winds with snow, and calm bluebird conditions. Conditions changed quickly and were quite variable. About 6 inches of fresh snow fell on the night of the 14th, and about 3 more on the night of the 15th, but in exposed locations, much of this snow was blown away, or was laid down as wind crustA crust is a hard layer of snow where liquid water has refrozen into grain fabric. Crusts usually result from sun, rain or wind.A Wind CrustA crust is a hard layer of snow where liquid water has refrozen into grain fabric. Crusts usually result from sun, rain or wind. is formed when wind deposits a hard packed layer of blown snow, or scours the surface. These are often found on windwardThe upwind side of an obstacle such as a ridge. Usually snow is eroded from windward slopes making them relatively safer. slopes. on exposed, leewardWind erodes snow from the windward (upwind) side of an obstacle and deposits snow on the leeward (downwind) side. Deposited snow looks smooth and rounded. You should always beware of recent deposits of wind drifted snow on steep slopes. slopes.

Wind:
Strong winds up high, with westerly gusts around 50 mph, punctuated by periods of complete calm. There was much evidence for strong winds in the previous days, with extensive wind crustA crust is a hard layer of snow where liquid water has refrozen into grain fabric. Crusts usually result from sun, rain or wind.A Wind CrustA crust is a hard layer of snow where liquid water has refrozen into grain fabric. Crusts usually result from sun, rain or wind. is formed when wind deposits a hard packed layer of blown snow, or scours the surface. These are often found on windwardThe upwind side of an obstacle such as a ridge. Usually snow is eroded from windward slopes making them relatively safer. slopes. coverage on most exposed locations above 6500′. The cornices built up on the ridges of sky pilot were enormous.

New Snow: 6-12″

Snow DensityThe mass of snow per unit volume, but often expressed as a percent water content. New fallen powder has a low densityThe mass of snow per unit volume, but often expressed as a percent water content. New fallen powder has a low density (3-10%), while heavy or wet snow is more dense (10-20%). (3-10%), while heavy or wet snow is more dense (10-20%).: Low

Avalanche Activity:
The new snowfall over the night of the 14th triggered many point releases and one big natural slabA relatively cohesive snowpack layer. A layer of snow stronger than underlying layers. which ran on a 40+ degree east facing slabA relatively cohesive snowpack layer. A layer of snow stronger than underlying layers. of bedrock, with the crown situated on a convexity. It looked to be about a foot thick. Besides these releases, there were no other notable indications of instability. Even so, we dug a few pits.

The first was on the south ridge of Sky Pilot at around 7800′, at the head of a good size 31-32 degree bowl. Compression tests yielded a CT7Q2 failure at 7cm in the wind affected new snow of the previous night, with a pretty soft slabby consistency. We also got a CT18Q2 failure on a layer of buried surface hoarFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dewFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dew. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried.. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried. at 40cm depth. Finally, we managed to get a CT25Q2 failure at 80cm depth, which failed on the interface between rounded snow, and the thick early season faceted snow layerA snowpack stratum differentiated from others by weather, metamorphism, or other processes.. Total snow depth here was 140cm. An extended column test indicated that none of these failures were inclined to propagate. The 7cm new snow layerA snowpack stratum differentiated from others by weather, metamorphism, or other processes. propagated halfway across the column.

Our second pit was on a 33 degree west facing slope above Bryan Lake, around 7200′. We got a CT4Q2 failure in the new snow at 15cm depth, with this snow forming a very soft, only slightly cohesive layer. We got another failure at 60cm depth along a layer of buried surface hoarFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dewFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dew. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried.. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried. at CT22Q2. ECT showed failures in these same locations, but, as before, neither fractureThe physical separation of the slabA relatively cohesive snowpack layer. A layer of snow stronger than underlying layers. from the bed surface and surrounding snow during the initiation of a slabA relatively cohesive snowpack layer. A layer of snow stronger than underlying layers. avalanche. propagated across the column. Total snow depth here was 170cm. The ubiquitous early season faceted layer was absent at this location, with essentially rounded snow all the way to the ground, and a uniformly increasing densityThe mass of snow per unit volume, but often expressed as a percent water content. New fallen powder has a low densityThe mass of snow per unit volume, but often expressed as a percent water content. New fallen powder has a low density (3-10%), while heavy or wet snow is more dense (10-20%). (3-10%), while heavy or wet snow is more dense (10-20%)..

With these results, we felt comfortable skiing fairly steep terrain, although the likelihood of some larger sluffs from the new snow seemed high.

Other Comments:

Observer: Doug Brinkerhoff