Avalanche Forecast
Issued: Dec 24th, 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.
dsaly,
Avalanche Canada
Flurries and wind will continue to develop slabs, expect to find more reactive deposits around ridges and in loaded terrain.
Summary
Confidence
Weather Forecast
Light to heavy snowfall is expected across southern BC Friday night through Sunday. An easterly arctic front meeting a southwesterly flow will produce enhanced snowfall where this clash occurs.
Friday night: Flurries 5-10 cm. Light and increasing southwest wind. Treeline temperatures near -16 and freezing levels at the valley bottom.
Saturday: Scattered flurries, 5-10 cm Moderate southwest wind. Treeline temperatures near -15 and temperatures dropping.
Sunday: Cloudy with scattered flurries, 5 cm. Light southwest wind and cold temperatures with a high of -20.
Monday: Mix of sun and cloud. Light winds from the southwest and cold temperatures with a high of -24.
Avalanche Summary
Explosives on Wednesday and Thursday triggered size 1-2 persistent slab avalanches at treeline elevations near Invermere, these failed on the crust-facet layer 40-70 cm deep.
On Wednesday, a few small (up to size 1) natural and human-triggered wind slab avalanches were reported.
Snowpack Summary
20-40 cm of recent storm snow sits on a surface hoar interface, which was likely more preserved at treeline and below. Wind is impacting loose snow and stiffer slabs may exist on leeward slopes and in wind-loaded terrain features. Low-density storm snow exists in sheltered terrain.
The upper snowpack overlies a substantial crust from 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.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- 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.
- Dial back your terrain choices if you are seeing more than 20 cm of new snow.
Problems
Wind Slabs
Reactive slabs continue to linger, especially where they sit above a surface hoar interface. Leeward wind-loaded slopes may host thicker and stiffer slabs. Be mindful of loose-dry sluffing in steeper wind-sheltered terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 40-120 cm over a crust that formed in early December. This layer has shown some reactivity in snowpack and explosives tests. New snow or smaller avalanches 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 25th, 2021 4:00PM
