Avalanche Forecast
Regions: Crawford, Dogtooth, East Purcell, Moyie, Purcells, St. Mary, West Purcell.
Avoid rocky, thin, and shallow areas where triggering slabs is most likely
Give cornices a wide berth. Cornice failure may trigger persistent weak layers resulting in very large avalanches
Confidence
Moderate
Avalanche Summary
On Sunday, evidence of several natural persistent slab avalanches triggered by cornice failure were observed up to size 2. See this MIN for details and photos of two of these avalanches.
Avalanche control triggered a size 2 persistent slab avalanche in a treeline feature at 1900 m on a north aspect.
If you head out in the backcountry, let us know what you see by submitting a MIN!
Snowpack Summary
2 to 10 cm of low-density snow sits atop a variety of surfaces, including surface hoar and facets on northerly aspects, a thin breakable sun crust on southerly aspects, and isolated wind slabs in the alpine. In sheltered areas, 20 to 75 cm of snow continues to settle.
A weak layer buried in early December can be found down 50 to 90 cm. On shaded slopes, it consists of weak surface hoar or faceted crystals, while on south-facing slopes, it combines a sun crust with facets.
The snowpack base is composed of a thick crust and facets in many areas.
Weather Summary
Monday Night
Clear skies. 5 to 20 km/h southwest ridgetop wind. Treeline temperature -5 °C.
Tuesday
Mainly clear. 15 to 30 km/h west ridgetop wind. Treeline temperature -3 °C.
Wednesday
Partially cloudy with light flurries, 1 to 3 cm. 20 to 40 km/h west ridgetop wind. Treeline temperature -8 °C.
Thursday
A mix of sun and cloud. 15 to 30 km/h west ridgetop wind. Treeline temperature -7 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Uncertainty is best managed through conservative terrain choices.
- Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
Avalanche Problems
Wind Slabs
As winds slowly increase, unconsolidated snow will be redistibuted into wind slabs in lee terrain. Wind slabs are most sensetive to triggering when they are newly formed. Look for signs of wind transport as you move through terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2
Persistent Slabs
Buried weak layers in the mid-pack persist and continue to produce sporadic persistent slab avalanches. While this avalanche problem is becoming more stubborn to trigger, it comes with serious consequences if you do.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 1 - 3