Avalanche Forecast
Regions: Dogtooth, East Purcell, Purcells, St. Mary.
Continue to give the recent storm snow time to settle and stabilize. New snow overlays a complex and generally weak snowpack.
Confidence
Moderate
Avalanche Summary
A natural avalanche cycle occurred on Tuesday with stormy weather. The majority of the reported avalanches were storm slab and wind slab releases on various aspects and elevations.
Deep persistent slab avalanches continue to be periodically reported throughout the region. Including a skier-triggered, fatal avalanche last Thursday.
Going forward we suspect natural avalanche activity to decrease. However, human-triggered slab avalanches will remain triggerable while the recent storm snow settles and bonds to underlying surfaces.
Snowpack Summary
Up to 50 cm of new snow since the weekend arrived with variable moderate winds, burying a layer of surface hoar in wind-sheltered terrain and a thin sun crust on steep south-facing terrain.
In general, the mid snowpack is facetted, with a number of surface hoar layers reported, especially at lower elevations.
The lower snowpack contains a widespread layer of large, weak facets and depth hoar in places. This layer sits at the base of the snowpack and has been responsible for a number of very large, destructive avalanches.
Snowpack depths at treeline are roughly between 100 and 200 cm, with the shallowest snowpacks found on the eastern edge of the Purcells.
Weather Summary
Wednesday night
Cloudy with clear periods / Moderate, northeast ridgetop winds / Treeline temperatures -20 to -25 C.
Thursday
Mostly sunny / Moderate, northeast ridgetop wind / Treeline temperatures -20 to -25 C.
Friday
Sunny / Light, northeast ridgetop wind, shifting to the southwest in the PM / Treeline temperatures -20 to -25 C.
Saturday
Sunny / Moderate, southwest ridgetop winds / Treeline temperatures -15 to -20 C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
Avalanche Problems
Storm Slabs
Reactive storm slab and wind slabs have formed with up to 50 cm of new snow and moderate to strong alpine winds. New snow my overlay a layer of surface hoar crystals or sun crust.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely - Very Likely
Expected Size: 1.5 - 3
Deep Persistent Slabs
The recent snow is overloading a very weak basal snowpack. Very large human triggered avalanches are likely in the alpine; especially in shallow, rocky, or thin to thick snowpack areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 2 - 4
Persistent Slabs
A number of weak layers of surface hoar remain a concern in the mid and lower snowpack.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1.5 - 3