Avalanche Forecast
Issued: Dec 23rd, 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
Storm slabs will likely be touchy to human triggering on Friday. Especially on wind-loaded leeward slopes.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
Light snow and flurries will continue in most areas as a cold northeasterly flow begins to assert itself at the surface. This will bring persistent cloudiness and continued light snowfall amounts through the Christmas weekend.
Thursday Night: A trace of new snow accompanied by moderate southwest wind. Treeline temperatures -8 and freezing level at the valley bottom.
Friday: Mix of sun and cloud withy flurries up to 5 cm. Generally light wind from the southwest. Treeline temperatures near -15 and freezing levels at the valley bottom. Temperatures continue to drop overnight.
Saturday: Cloudy with 5-10 cm accompanied by moderate southwest wind. Treeline temperatures near -15 and freezing levels at the valley bottom.
Sunday: Cloudy with some flurries up to 5 cm. Light winds from the southwest and colder temperatures at -25.Â
Avalanche Summary
No recent reports by Thursday afternoon.Â
On Wednesday, a few natural and human-triggered wind slab avalanches up to size 1 were reported.Â
Natural avalanche activity may taper on Friday, the storm slab could be primed for human triggering. Loose-dry sluffing may be seen from steep terrain features.
Snowpack Summary
20-30 cm of recent storm snow sits on a surface hoar interface and could be fairly reactive to human triggers. Stiffer slabs may exist on leeward slopes and behind terrain features due to wind loading. Low-density storm snow exists in sheltered terrain.
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
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Start with conservative lines and watch for clues of instability.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
Problems
Storm Slabs
Reactive storm slabs continue to linger, especially where they sit above a surface hoar interface. Leeward wind-loaded slopes may host thicker and stiffer slabs.
Loose-dry sluffing will likely exist on steeper wind-sheltered slopes and terrain features.
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 24th, 2021 4:00PM
