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
Loose, dry snow is providing excellent conditions. Assess conditions as you travel, reactive slabs may be found where snow feels stiff or more cohesive.
Summary
Confidence
Weather Forecast
Saturday night: Scattered flurries, 5-10 cm. Moderate gusty southerly winds. Treeline temperatures near -10 and freezing levels at the valley bottom.
Sunday: Unsettled and windy with scattered flurries, up to 5-10 cm. Moderate south wind and temperatures dropping from -13.
Monday: Cold and cloudy with sunny breaks. Light southwest wind and a high of -18.
Tuesday: Cold, mostly cloudy, and isolated flurries. Light north wind and a high temperature of -20.
Avalanche Summary
Oh Friday, small (size 1-1.5) slab avalanches were reactive to skiers. Explosives triggered larger (size 2.5) avalanches including 2 avalanches which failed on the early December crust with crowns 80-120 cm deep.
On Thursday, several natural and skier-controlled storm slab avalanches up to size 2 were reported, and explosives triggered slab avalanches to size 2.5; avalanches ranged from 20-60 cm deep.
Snowpack Summary
25-60 cm cold, dry snow arrived Christmas with light southwest wind, ongoing flurries are expected through Sunday. Cold temperatures and calm winds will keep snow light and fluffy, but snow will be redistributed easily with little wind. Sluffing is to be expected in steep terrain.
In total, 30-70 cm snowfall over the week reportedly covered a thin freezing rain crust and a surface hoar interface, which has been responsible for recent storm slab avalanches.
A crust from early December is now 50-120 cm below the surface, and is found up to 2300 m. A layer of weak facets (sugary snow) has been reported above and below this crust, and is the layer of concern in our persistent avalanche problem.
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
- 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.
- Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Problems
Storm Slabs
Some areas collected upwards of 50 cm through Christmas day with flurries continuing into Sunday. New snow fell with light winds and is still quite loose and dry, however slab avalanches could become reactive with even minor input from the wind. Expect to initiate loose-dry sluffing in steeper terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A crust from early December is now 50-120 cm below the surface, and is found up to 2300 m. A layer of weak facets (sugary snow) has been reported above and below this crust. Explosives have triggered large (size 2.5) avalanches failing on this layer as recent as Friday, Dec 24. New snow and wind loading, or a heavy 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
