Avalanche Forecast
Issued: Dec 5th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
Wind slab formation will be of greatest concern in the south of the region, where upwards of 20 cm of low density snow sits on top of a crust. Elsewhere, thinner isolated pockets can still be surprisingly reactive as they are likely poorly bonded to underlying surfaces.
Summary
Confidence
Moderate - Uncertainty is due to limitations in the field data. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.
Weather Forecast
Sunday night: A trace of new snow. Moderate southwest wind. Treeline temperature around -13.
Monday: Flurries around 5 cm. Light to moderate northwest wind. Treeline high temperatures around -8.
Tuesday: Cloudy with flurries starting in the afternoon. Strong southwest wind. Treeline high temperatures around -3.
Wednesday: New snow 10-20 cm. Strong southwest wind. Treeline high temperatures around -8.
Avalanche Summary
On Saturday, some loose dry sluffing and thin soft slab reactivity were seen in steep terrain and near ridge crests in the neighboring Sea to Sky region. The most recent reports we have from the inland are of explosives producing a size 2 wind slab avalanche in the Hurley on Thursday.
Snowpack Summary
5-20 cm of new low density snow may sit over a widespread layer of small surface hoar crystals which we will continue to monitor going forward. This sits over wind affected snow in the alpine and a thick, supportive crust below 1800 m. Between 1800-2100 meters, this crust exists shallowly buried by wind affected snow.Â
A couple of buried weak layers produced large avalanches during a previous storm. Snowpack models and observations in the neighboring Sea to Sky region indicate that these layers have been reset by previous rain at treeline, but uncertainty remains around their status in the alpine. These include a layer of surface hoar down an estimated 90-120 cm and deeper crust/facet combo layer.
Average snowpack depths in the alpine are now likely closer to 150-200 cm. Below treeline, depths of 30-50 cm have been reported around 500 m, decreasing dramatically with elevation, and still below threshold for avalanches in many areas. Early season hazards such as rocks, stumps, and creeks are still a concern below the alpine.
Terrain and Travel
- Be carefull around freshly wind loaded features.
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
- Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
- Keep in mind the crust offers an excellent bed surface for avalanches.
Problems
Wind Slabs
Small inputs of new snow along with moderate wind will feed wind slabs in the alpine and upper treeline. Watch for fresh deposits in lee terrain features.
Low density surface snow that hasn't formed a slab may also slide easily on a slippery crust.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A buried weak layer may exist at upper elevations. Large loads such as wind slab releases have potential to trigger this layer to produce very large, destructive avalanches.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 6th, 2021 4:00PM
