Avalanche Forecast
Regions: Crawford, Dogtooth, East Purcell, Moyie, Purcells, St. Mary, West Purcell.
Rocky, wind-affected areas are a prime suspect for large, human-triggered avalanches.
Seek out sheltered, moderate-angled slopes for the best and safest riding.
Confidence
Moderate
Avalanche Summary
On Tuesday, a large skier-triggered avalanche (see this MIN) indicated reactive wind slabs failing on facets are a significant issue in alpine and treeline terrain.
On Wednesday, explosive control near Invermere produced numerous size 1 deep persistent slabs from steep, treeline terrain.
Both of these avalanche problems will continue into Friday. Steep, rocky, wind-loaded areas are prime suspects for either of these dangerous instabilities!
Snowpack Summary
5 to 20 cm of new snow has fallen in the past 24 hours. Accompanying southwest winds have likely redistributed this new snow, forming deeper deposits on leeward slopes at higher elevations.
A layer buried in early December is found roughly 20 to 90 cm below the surface. This layer varies, consisting of weak surface hoar or facetted crystals on shaded slopes and a sun crust with facets on south-facing slopes.
The base of the snowpack is made up of a thick crust and facets in many areas.
Weather Summary
Thursday Night
Cloudy with up to 5 cm of new snow. 15 to 40 km/h southwest ridgetop wind. Treeline temperature -5 °C.
Friday
A mix of sun and cloud with up to 3 cm of new snow. 10 to 30 km/h southwest ridgetop wind. Treeline temperature -6 °C.
Saturday
Cloudy with up to 10 cm of new snow. 25 to 50 km/h southwest ridgetop wind. Treeline temperature -4 °C.
Sunday
Mostly cloudy with up to 2 cm of new snow. 10 to 30 km/h southwest switching to northeast ridgetop wind. Treeline temperature -5 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid freshly wind-loaded features, especially near ridge crests, rollovers, and in steep terrain.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avalanche Problems
Wind Slabs
Fresh, reactive wind slabs exist in lee and cross-loaded areas from yesterday's snowfall and wind.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2
Persistent Slabs
In the mid-snowpack, buried surface hoar or facets may pose a risk on north-facing slopes, while a buried sun crust could be reactive in south-facing areas.
In shallow snowpack areas, facets at the base of the snowpack are generally weak.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 2.5