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 triggers 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 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.
Saturday: Cloudy with scattered flurries moderate southwest wind. Treeline temperatures near -10 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 -13.Â
Avalanche Summary
On Thursday several size 2 natural slab avalanches were reported. Numerous explosive triggered storm slabs were also seen up to size 2.Â
Natural avalanche activity may taper on Friday but the storm slab could be primed for human triggering.Â
Snowpack Summary
20-30 cm of recent storm snow overlies a thin freezing rain crust and a surface hoar interface.
Below the new snow exists a well-consolidated snowpack that overlies a substantial crust that formed in early December. This crust is approximately 70-100 cm below the surface, 10 cm thick on average, and is present across all aspects to at least 2300m. A layer of weak facets (sugary snow) has been reported above this crust.Â
The lower snowpack is composed of several early-season crusts. Snow depths at treeline average 150-200 cm. Below 1800 m the snowpack remains relatively shallow with 80-120 cm on average. The deepest snowpack can be found in the Kootenay Pass area.
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.
Surface hoar has been reported below the new snow. This could make slabs more widespread and increase the reactivity and propagation potential.
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 60-100 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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 24th, 2021 4:00PM
