Avalanche Forecast
Issued: Dec 22nd, 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.
swerner,
Avalanche Canada
New snow accompanied by strong southwest wind will likely build fresh and reactive storm slabs, especially on leeward slopes that are wind-loaded.
Summary
Confidence
Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system. Forecast snowfall amounts are uncertain.
Weather Forecast
Continued snow through the Christmas holidays. Possible heavier snowfall amounts in the Southern part of the region on Thursday with the passing cold front. Â
Wednesday Night: 5- 10 cm of new snow accompanied by strong ridgetop wind from the southwest. Alpine temperatures near -7 and freezing levels 900 m.
Thursday: New snow throughout the day, with 10-15 cm accumulation. Strong ridgetop wind from the southwest. Alpine temperatures near -5 and freezing levels 1200 m.Â
Friday: Broken skies with flurries 5 cm with moderate to strong southwest wind. Alpine temperatures near -10 and freezing levels valley bottom.
Saturday: Mostly cloudy with flurries 5 cm. Gusty ridgetop winds from the South and temperatures dropping to -12 with freezing levels valley bottom.Â
Avalanche Summary
On Wednesday, a few natural and human-triggered wind slab avalanches up to size 1 were reported.Â
New snow and cranking wind will likely form reactive slab avalanches on Thursday. Loose-dry sluffing may be seen from steep terrain features.
Snowpack Summary
New snow and wind will likely build reactive storm slabs. Older wind slabs at upper elevations below ridgecrest may continue to be touchy with the additional load. Low-density storm snow exists in sheltered terrain.Â
Below the new snow exists a well-consolidated upper snowpack which overlies a substantial crust that formed in early December. This crust is approximately 60-120 cm below the surface, 10-30 cm thick on average, and is present across all aspects to at least 2300 m. A layer of weak facets (sugary snow) has been reported above this crust. Snowpack tests are generally showing hard results on this interface.
A late October facet/crust layer of concern sits at the bottom of the snowpack above 1900m. Although this layer has been trending less reactive, it remains on our radar.
The snowpack depth at treeline is around 120-250 cm. The deepest snowpack can be found in the southern half of the region.Â
Terrain and Travel
- Watch for fresh storm slabs building throughout the day.
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
Problems
Storm Slabs
Reactive storm slabs will build through the day with new snow and strong southwest wind. Leeward wind-loaded slopes may host thicker and stiffer slabs.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 60-120 cm over a crust that formed in early December. This layer has shown some reactivity in snowpack tests. The new snow may add enough stress to trigger a persistent slab.
At the base of the snowpack above 2200 m, a layer of depth hoar lingers. Avalanches-in-motion have the potential to step down to this layer.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 23rd, 2021 4:00PM
