Avalanche Forecast
Regions: Dogtooth, East Purcell, Purcells.
While conditions are gradually improving with cooling temperatures, very large persistent slab avalanches may remain triggerable in areas not capped by a thick surface crust.
Confidence
Moderate
Avalanche Summary
Several naturally triggered persistent slab avalanches up to size 3 (very large) and numerous wet loose avalanches up to size 2.5 were reported on all aspects and elevations on Monday.
On Tuesday, a machine-triggered size 1.5 persistent slab was reported on a north aspect in the alpine north of Golden and explosives produced persistent slab and loose wet avalanches size 1.5-2 near Invermere.
Snowpack Summary
A skiff of new snow now sits over predominantly crusty surfaces. Dry snow may be found on high north aspects in the alpine, and moist surfaces may persist at low elevations.
A widespread, hard crust down 40 - 110 cm with weak facets above continues to be the primary layer of concern for human triggering of very large persistent slab avalanches.
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
Wednesday night
Cloudy with isolated flurries, 3 to 5 cm of snow. 10 to 20 km/h west ridgetop wind. Treeline temperature 0 °C. Freezing level 1000 m.
Thursday
Mostly cloudy with isolated flurries, 3 to 8 cm of snow (above 1400m). 20 to 30 km/h northwest ridgetop wind. Treeline temperature -1 °C. Freezing level 1800 m, dropping to valley bottom overnight.
Friday
Mostly cloudy with isolated flurries, 2 to 5 cm of snow. 5 to 10 km/h southeast ridgetop wind. Treeline temperature -5 °C. Freezing level 1500 m, dropping to valley bottom overnight.
Saturday
Mostly cloudy with isolated flurries, 2 to 5 cm of snow. 5 to 10 km/h southeast ridgetop wind. Treeline temperature -5 °C. Freezing level 1500 m, dropping to valley bottom overnight.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Conditions may have improved, but be mindful that deep instabilities are still present.
- 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.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Avalanche Problems
Persistent Slabs
A crust with weak facets above is down 40 to 110 cm. Steep or convex terrain features with a shallow or thin to thick snowpack at treeline and above are the most likely places to trigger this layer.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 2 - 3.5
Loose Wet
If triggered, loose wet avalanches may step down to deeper layers, resulting in very large avalanches.
Aspects: All aspects.
Elevations: Below Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5