Avalanche Forecast
Issued: Dec 25th, 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.
dsaly,
Avalanche Canada
Reactive storm slabs may linger as snowfall tapers through Sunday. Be aware of ongoing slab development in windy areas.
Summary
Confidence
Weather Forecast
Saturday night: Cold with starry breaks and isolated flurries, 5-10 cm. Light, gusty south wind. Overnight lows dropping to -28.
Sunday: Cloudy with isolated flurries, up to 5 cm. Light to moderate southeast wind. High temperature of-22, possible inversion.
Monday: Cold and cloudy with sunny breaks. Light, wind and cold temperatures with a high of -21.
Tuesday: Mix of sun, cloud, and isolated flurries. Light, gusty winds and cold temperatures with a high of -22.
Avalanche Summary
On Friday, a small (size 1) storm slab was reported triggered by skier traffic. Otherwise, riders reported loose-dry sluffing with the new snow.
On Thursday, explosives triggered a few small (size 1) storm slab avalanches. On Wednesday, the South Rockies field team reported several wind slabs that appeared to have slid on the early December crust and up to size 2.
Snowpack Summary
25-45 cm low density snow arrived Christmas morning with storm totals over 60-100 cm in the last week. Gusty winds have produced variable storm slabs and cross-loaded terrain features. In some wind exposed areas surfaces have likely been stripped back down to older wind slabs and the early December crust. Sheltered areas may still hold loose snow. A lot of variability exists.
A crust from early December is now 60-100 cm below the surface, and is found up to 2400 m. A layer of weak facets (sugary snow) has been reported above and below this crust. This is the layer of concern in our persistent avalanche problem, snowpack tests are generally showing hard results on this interface, however, areas, where avalanches have recently failed on this crust, continue to be problematic once reloaded with new snow.
Below 2300 m, several early-season crusts make up the lower snowpack. Snowpack depths range from 80-150 cm at treeline elevations and taper quickly below 1900m.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
- 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
Ongoing flurries and strong winds means ongoing slab development. Slabs will be more reactive on leeward (wind-loaded) slopes where deposits are deeper and stiffer. Expect to initiate 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 60-100 cm over a crust that formed in early December. This layer has produced large avalanches with explosive triggers and has shown reactivity in snowpack tests. A larger trigger such as a skier or snowmobile, may add enough stress to trigger a persistent slab.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 26th, 2021 4:00PM
