May 9, 2014 update. The Olson Gulch avalanche accident report is now available online:
On Saturday May 3 at 10 am, an experienced solo backcountry skier was caught in a wet snow avalanche in the southern portion of the Flint Creek range in the Olson Gulch drainage 10 air miles northwest of Anaconda, MT. He was carried approximately 760 feet down the path, strained through trees and was partially buried against a tree at the mid point of the avalanche. Although buried up to his chest, he was able to free himself enough to make a cell phone call to EMS and local SAR. He reported having back and leg injuries and unable to extricate himself. SAR arrived on scene at approximately 1240 and began extrication efforts. Butte Life Flight paramedics and nurses also arrived after post holing uphill to the site from the LZ. The individual died at the scene from injuries related to trauma.
The Avalanche Classification is: WL-ASu-D2-R2-I; a wet, loose snow, unintentionally triggered avalanche that could bury, injure or kill a person. The size of the avalanche is small relative to the historic path and the snow released on the new snow/old snow interface.
The avalanche start zone is at 7890 feet on an east-northeast aspect. The avalanche was reported to be 15-30 feet wide X 1300 feet long (GE est). The terminus of the slide is at 7160 feet. The alpha angle of the avalanche is 30 degrees.
The nearest representative SNOTEL site (Warm Springs at 7800 feet) recorded a temperature of 54 degrees at 10 am May 3. The previous 48 hour temperatures remained above freezing for the first time this spring.
We will post more detailed information at a later date.
The avalanche coordinates are: N46 11.83 X W113 06.91 in the Olson Gulch drainage
Late season snowpack conditions have been exceptional for backcountry skiing. This spring has stayed relatively cool with the first real warm up occurring last week at the higher elevations. When temperatures remain above freezing for as long as they appeared to in this case, the snowpack can become unstable.
Our thoughts are with the friends and family of the individual.
Spring avalanche safety considerations:
When it snows:
Assess how well storm snow bonds to the old snow surface. New snow last weekend was failing easily on a hard crust that formed during the warmer temperatures prior to the storm. Many natural avalanches were observed in the southern Swan and Mission mountains last weekend with the new snow failing easily on this interface.
Fresh wind slabs can be very sensitive during and for a few days after a storm.
Cornices are scary looking for a good reason. Steer clear of them, they have a nasty reputation for breaking further back when they get this big.
When it warms up:
Wet, loose snow avalanches can entrain enough snow to cause step down slab avalanches that tend to be more destructive (unsurvivable).
Wet slab avalanches are a troublesome beast so when mountain temperatures remain above freezing for a night or two, don’t trust anything steep and loaded.
Cornices are not only scaring looking, they also fail easily all by themselves when it warms up. A large cornice dropping onto a big slope can trigger large slab avalanches, wet and dry, this time of year.
Overall stability conditions are easily monitored by paying attention to the aspect and air temperature. Move to more shaded northerly terrain as the temperature warms above freezing. Avoid being on or under open steep terrain when you see pinwheels or small point release avalanches peeling off steeper terrain. When you start punching through to your boot tops move to cooler/shaded areas where the snow is more stable.
When the ski areas are closed, the in-bounds terrain is backcountry terrain and you must plan accordingly. If you are unsure about a resort’s uphill policy, or where to access public land from a resort, the time-honored Montana tradition is to ask the landowner.
We will continue posting public observations as we receive them. You can submit an observation directly from our website.
Posted May 5 by Steve Karkanen