Avalanche Forecast
Issued: Nov 28th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
dboucher,
Avalanche Canada
Recent snowfalls at higher elevations have developped storm slabs that could trigger deeper weak layers and produce large avalanches.
Summary
Confidence
Weather Forecast
A weak ridge of high pressure will bring a break between storms with mainly quiet conditions for Monday.
Sunday night: Flurries; 10-15 cm. Moderate to strong southwest winds. Alpine low temperatures -3 C with freezing levels going down to 1600 metres.
Monday: Mainly cloudy with isolated flurries. Moderate southwest winds. Alpine high temperatures -3 C with freezing levels steady at 1600 metres.
Tuesday: Heavy snow or rain; 15-30 cm. Strong southwest winds. Alpine high temperatures -3 C with freezing levels at 1700 metres.
Wednesday: Wet snow mixed with rain; 25-35 cm. Strong southwest winds. Alpine high temperatures +1 C with freezing levels at 2200 metres.
Avalanche Summary
A few natural and triggered storm slabs avalanche (size 1) and loose wet were reported Saturday. Also, large avalanches sliding on recently buried surface hoar and deeper buried crusts have been observed in the region as well as in the neighboring South Coast Inland.
Snowpack Summary
Recent snowfalls and strong southerly winds have created reactive storm slabs in leeward alpine and treeline features. The new snow also buried deeply a surface hoar layer observed in between 1800 and 2100 meter and a combo of thick crust/ facets present up to 2200 meters. Surprising large avalanches sliding on these weak layers have been reported over the last few days and, if upper elevations slopes haven't avalanched already, further loading by snow and wind or human triggers could initiate avalanche activity on these layers.
Average snow depths at treeline are now likely closer to 150-200 cm; 250+ cm in the alpine. Snowpack depths decrease dramatically below treeline and may still be below threshold for avalanches in some areas. Early season hazards such as rocks, stumps, and creeks are still a concern at these lower elevations.
Terrain and Travel
- In times of uncertainty conservative terrain choices are our best defense.
- Be aware of the potential for large, deep avalanches to run full path or even longer.
- If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
Problems
Storm Slabs
Recent snowfalls at higher elevations have developped storm slabs above a weak layer of surface hoar and/or a deeper crust. Thicker storm slabs are likely to be found in lee terrain features. Avalanches have the potential to be larger than expected if they step-down on the deeper combo crust / facets.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A deep weak layer affecting alpine areas could result in very large, full-path destructive avalanches.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Nov 29th, 2021 4:00PM
