Avalanche Forecast
Issued: Dec 20th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
ldreier,
Avalanche Canada
Avalanche activity on the persistent weak layers has decreased. However, it is important to stay vigilant. Maintain good travel habits and check out our forecaster blog on managing a persistent slab.
Come prepared with lots of warm layers, hot drinks and a headlamp when venturing out. Cold temperatures and short days can turn even small incidents like broken equipment into a very bad time.
Summary
Confidence
Moderate
Avalanche Summary
On Monday, two natural size 2 wind slab avalanches were observed, and several smaller wind slabs released in steep terrain. A size 2 slab avalanche was triggered remotely by riders, and two small size 1 wind slabs were triggered by skiers. Explosive control resulted in a small slab avalanche.
On Sunday, skiers triggered several small avalanches of size 1 below treeline about 40 cm deep. A small natural avalanche released on a northern aspect around 2000 m and there were several reports of whumpfing and shooting cracks.
On Saturday, skiers triggered a size 1 wind slab avalanche on a southeast aspect at 2300 m.
Snowpack Summary
Snowpack depths at treeline range from 100-150 cm. In the alpine, snowpack depths are highly variable from extensive wind-affect in many locations.
Surface: 5-15 cm of recent snow overlies 5-8 mm surface hoar in sheltered areas. On steep solar slopes, new snow overlies a sun crust. Moderate westerly winds have built thin wind slabs in alpine lees.
Upper-pack: Cold temperatures are faceting the upper snowpack. 40-50 cm settling snow overlies a weak layer of 5 mm surface hoar in sheltered and shaded terrain and a sun crust on sunny south-facing slopes.
Mid-pack: Buried 60-90 cm deep, is a persistent weak layer of surface hoar, crust, and faceted crystals. This layer has been most reactive at treeline between 1700-2200 m, but it was also observed as low as 1450 m and on all aspects.
Lower-pack: Below the mid-November layer is a generally weak, faceted snowpack.
Weather Summary
Tuesday Night
Decreasing cloud coverage, trace of snow, 20 km/h northerly wind, temperature low at -32 °C.
Wednesday
Mix of sun and some clouds, trace of new snow, 20 km/h northeast wind, temperature high around -26 °C.
Thursday
Sunny, 10 km/h easterly wind, temperature high at -27 °C.
Friday
Cloudy, 5-10 cm new snow, 40 km/h southerly wind, temperature high at -20 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Avoid making assumptions about this layer based on the presence of aggressive tracks on adjacent slopes
Problems
Persistent Slabs
There are two persistent weak layers within the snowpack: 30-50 cm of snow covers a weak layer of surface hoar on shaded aspects and a crust on steep solar aspects; many avalanches failed on this layer last week.
A second weak layer consists of surface hoar and facets from mid-November and is buried 60-90 cm in the region; this layer has recently surprised both professionals and recreationists with large human-triggered avalanches.
Read our featured blog to learn more about how to manage a persistent slab problem when travelling in the backcountry.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Moderate westerly winds have built thin wind slabs at higher elevations. Be cautious when transitioning into wind-affected areas, especially around ridge crests and roll-overs in steep terrain.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 21st, 2022 4:00PM
