Avalanche Forecast
Issued: Dec 24th, 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
A suspicious layer of surface hoar is buried under the new snow, and responsible for recent avalanches - dig down and investigate the slab properties of the new snow and bond with the old surface.
Summary
Confidence
Weather Forecast
Light to heavy snowfall is expected across southern BC Friday night through Sunday. An easterly arctic front meeting a southwesterly flow will produce enhanced snowfall where this clash occurs; a band of heavy snowfall is forecasted to clip the Kootenay Pass area.
Friday Night: Flurries, 10-20 cm new snow overnight, Kootenay pass is expected to see the deepest deposits. Moderate and gusty southerly winds. Treeline temperatures near -10 and freezing level at valley bottom.
Saturday: Ongoing scattered flurries, 5-10 cm. Moderate gusty southerly winds. Treeline temperatures near -10 and freezing levels at the valley bottom.
Sunday: Cloudy and flurries, up to 7-12 cm. Light winds from the southwest and colder temperatures at -13.
Monday: Cloudy with sunny breaks. Light winds from the southwest and colder temperatures at -13.
Avalanche Summary
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
20-40 cm of recent storm snow overlies a thin freezing rain crust and a surface hoar interface. Recent westerly winds have pressed surfaces and loaded leeward features.
The upper snowpack overlies a substantial crust from 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.
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.
- Dial back your terrain choices if you are seeing more than 25cm of new snow.
Problems
Storm Slabs
Recent slab avalanches have failed with the new snow bonding over a layer of surface hoar. With ongoing flurries and gusty winds, slab avalanches may continue to be reactive to human triggers especially on leeward (wind-loaded) slopes that host thicker and stiffer slabs. Be mindful of 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 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 25th, 2021 4:00PM
