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 Wind Slabs and Persistent Slabs.
swerner,
Avalanche Canada
Touchy wind slabs will likely exist on Friday. Be conservative with your terrain choices and watch for signs of instability like natural avalanches, cracking and hollow sounding snow in the upper snowpack.
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: New snow 5-10 cm accompanied by moderate southwest wind. Treeline temperatures -8 and freezing level at the valley bottom.
Friday: New snow 5-10 cm with strong southerly winds. Treeline temperatures near -10 and freezing levels near 800 m. Temperatures continue to drop overnight.
Saturday: Cloudy with 5-15 cm accompanied by moderate southwest wind. Treeline temperatures near -20 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 new avalanches were reported on Thursday afternoon.Â
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.Â
Natural avalanche activity may taper on Friday but wind slabs could be primed for human triggering.Â
Snowpack Summary
15-25 cm of recent storm snow accompanied by strong to extreme winds have likely formed wind slabs at most elevations in open terrain.Â
Wind exposed areas have likely been stripped back down to the early December crust and old wind slabs. A lot of variability exists.
Below the surface exists a well-consolidated upper snowpack that overlies a substantial crust that formed in early December. This crust is approximately 50-90 cm below the surface, 20 cm thick on average, and is present across all aspects to at least 2400 m. A layer of weak facets (sugary snow) has been reported above this crust. 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.Â
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
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- 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
Wind Slabs
Strong to extreme winds primarily from the South combined with the recent storm snow has likely formed stiff and reactive wind slabs.
Aspects: North, North East, East, North West.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 50-90 cm over a crust that formed in early December. This layer has produced large avalanches from explosive triggers and has shown reactivity in snowpack tests. The new snow may add enough stress to trigger a persistent slab.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 24th, 2021 4:00PM
