Avalanche Forecast
Regions: Dogtooth, East Purcell, Purcells, West Purcell.
Danger ratings have declined but the inherently weak and dangerous snowpack structure remains.
A moderate rating reflects the possibility of large, high-consequence human-triggered avalanches. Remain diligent in your terrain selection by avoiding steep, rocky, wind-affected terrain and choosing small, low-consequence features.
Confidence
Moderate
Avalanche Summary
Near Panorama ski resort on Wednesday, a natural wind slab released from a southeast aspect in the alpine, stepping down to a mid-snowpack persistent weak layer at treeline elevation, resulting in a size 2 avalanche.
Earlier in the week, strong solar radiation triggered several natural size 2 to 3 deep persistent slabs on south aspects, reported from rocky alpine and treeline features between 1900 and 2700 m. Additionally, a variety of solar-triggered loose wet avalanches up to size 2 were observed from steep, rocky slopes.
Last Sunday, a remotely triggered size 2 persistent slab avalanche was reported on a NW aspect at 2400 m, failing down 70 cm on facets and triggered from 30 m away.
Snowpack Summary
At upper elevations, a dusting of new snow overlies a crust on solar aspects, faceted snow and surface hoar up to 10 mm in shaded and wind-sheltered areas, and wind-affected surfaces in exposed areas.
In the middle of the snowpack, there are at least a couple of lingering persistent weak layers, including surface hoar in wind-sheltered terrain and a sun crust on south aspects. Activity on these layers has tapered off but still remains a concern in isolated areas.
The lower snowpack is made up of a widespread layer of large, weak facets and/or depth hoar crystals. This weak layer has been responsible for a number of recent very large, destructive avalanches and will likely continue to be a concern for the rest of the season.
Weather Summary
Friday night
Cloudy with clear periods. Alpine temperatures drop to a low of -9 °C. Ridge wind southwest 10 to 30 km/h. Freezing level at valley bottom.
Saturday
A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -6 °C. Ridge wind northwest 10-25 km/h. Freezing level rises to 1500 metres.
Sunday
Sunny with cloudy periods. Alpine temperatures reach a high of -7 °C. Ridge wind light from the east. Freezing level rises to 1500 metres.
Monday
Sunny with cloudy periods. Alpine temperatures reach a high of -8 °C. Ridge wind light from the west. Freezing level rises to 1200 metres.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- It's critical to stay disciplined and choose only well supported, low consequence lines.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
- Minimize your exposure time below cornices.
Avalanche Problems
Deep Persistent Slabs
The base of the snowpack remains very weak. Very large human-triggered avalanches are possible at treeline and above. Avoid thin, rocky start zones and shallow areas with variable snowpack depth where you are most likely to trigger this layer. Give careful consideration to the slopes overhead as large avalanches may run well into the runout zone or into lower-angle terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 2.5 - 4
Persistent Slabs
Lingering weak layers are present at all elevations and on various aspects. On shaded slopes, these layers generally present as surface hoar or facets, while on sun-exposed slopes, they appear as facets and a crust.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Unlikely - Possible
Expected Size: 1.5 - 3