Avalanche Forecast
Regions: Dogtooth, East Purcell, Purcells.
Very large persistent slab avalanches remain likely to human trigger, especially at treeline and above.
Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
Confidence
Moderate
Avalanche Summary
Numerous naturally triggered persistent slab and deep persistent slab avalanches up to size 3.5 (very large) were reported on all aspects and elevations on Sunday.
Snowpack Summary
A weak surface crust forming overnight will break down quickly throughout the day.
A widespread, hard crust down 40 - 110 cm with weak facets above continues to be the primary layer of concern for natural and human triggering of very large persistent slab avalanches.
Cornices have become large and looming, and are more likely to fail during periods of warming.
The bottom of the snowpack is generally weak and faceted, with the potential to produce very large avalanches. The most likely areas to trigger this deeply buried weak layer are steep, rocky areas in the alpine with a shallow or thin to thick snowpack.
Weather Summary
Monday Night
Clear skies. 10 to 20 km/h southwest ridgetop wind. Treeline temperature -2 °C. Freezing level 1000 m.
Tuesday
Mix of sun and cloud. 10 to 20 km/h southwest ridgetop wind. Treeline temperature 3 °C. Freezing level 2400 m.
Wednesday
Mix of sun and cloud with isolated flurries, 0 to 3 cm of snow (above 1700 m). 10 to 20 km/h west ridgetop wind. Treeline temperature -1 °C. Freezing level 2000 m.
Thursday
Mix of sun and cloud with isolated flurries, 3 to 5 cm of snow (above 1400m). 10 to 20 km/h west ridgetop wind. Treeline temperature -3 °C. Freezing level 1700 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
- Be aware of the potential for large, deep avalanches to run full path or even longer.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
- Cornice failure may trigger large avalanches.
Avalanche Problems
Persistent Slabs
A crust with weak facets overtop is down 40 to 110 cm. Very large human triggered avalanches occurring on this layer are likely on Tuesday, especially at treeline and above.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 2 - 4
Deep Persistent Slabs
A widespread weak layer exists at the bottom of the snowpack. Large triggers, such as falling cornices or smaller avalanches in motion may have the potential to trigger this deeply buried weak layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 3 - 4
Loose Wet
If triggered loose wet avalanches may step down to deeper layers, resulting in very large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 2.5