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
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 -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 -15.
Avalanche Summary
On Thursday, numerous storm slabs were triggered by machines and explosives. The majority of them were size 2 with one size 3 reported.
Natural avalanche activity may taper on Friday but slab avalanches likely remain primed for human triggering.
Snowpack Summary
30 to 50 cm of recent storm snow sits above a surface hoar interface and pockets of old wind slab. Low-density storm snow exists in wind-sheltered 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 90-150 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.
The lower snowpack consists of a variety of early-season crusts and mainly moist snow. Snowpack depths range from 100-200 cm at treeline elevations and taper quickly below 1800 m.
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 buried persistent weak layers.
Problems
Storm Slabs
Storm slabs could be reactive to human triggering on Friday, especially on leeward (wind-loaded) slopes that 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 100-150 cm over a crust that formed in early December. There have been reports of natural and human-triggered avalanches on this layer during the last storm in areas where the overlying slab is shallower.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 24th, 2021 4:00PM
