Avalanche Forecast
Issued: Dec 11th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Storm Slabs.
lbaker,
Avalanche Canada
Continue to make conservative terrain choices while storm snow settles and stabilizes. Though natural avalanche activity has tapered off the risk of humans triggering avalanches remains.
Summary
Confidence
Avalanche Summary
On Saturday numerous storm slab avalanches were observed up to size 2 on an interface within the storm snow and on the Dec 5 surface hoar. Whumpfing and cracking were observed throughout the region.
Friday two remotely triggered size 2 persistent slab avalanches were reported failing on the persistent weak layers buried mid November. Activity occurred from 1800-2300 mostly in sparsely treed terrain.
Snowpack Summary
Moderate southwest ridgetop winds have redistributed 40 - 50 cm of storm snow into deep pockets at higher elevations. On south facing slopes this new snow has fallen on a sun crust and in sheltered terrain it sits over a layer of surface hoar.
Buried 60 to 90cm deep, a persistent layer of surface hoar, crust, and faceted crystals is the primary concern within the snowpack. 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.
Snowpack depths are highly variable and range from 90cm at treeline to 200cm in the alpine in wind-affected locations.
Weather Summary
Sunday Night
Mainly cloudy with isolated flurries. Light northerly ridge winds. Alpine temperatures, high of -5. Freezing levels drop from 900 m to valley bottom overnight.
Monday
Mix of sun and cloud with isolated flurries. Light northerly ridge winds. Alpine temperatures, high of -8. Freezing levels rise to 700m in the southern part of the region.
Tuesday
Mainly sunny with a few clouds. Light to moderate easterly ridge winds. A weak alpine inversion brings alpine temperatures around -4 while the valley bottom remains -10.
Wednesday
Mix of sun and cloud with isolated flurries. Light to moderate northerly ridge winds. Alpine temperatures, high of -9.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Give the new snow time to settle and stabilize before pushing into bigger terrain.
Problems
Persistent Slabs
A weak layer of surface hoar and facets from mid November is buried 50 to 90cm deep. Two notable large and surprising avalanches occurred on this layer on Friday.
Use extra caution at treeline where this layer is more prominent and look for signs of instability like shooting cracks, whumpfing and recent avalanches. Read our newest blog to learn more about this concerning layer and how to manage it.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Storm Slabs
Southwest winds have redistributed recent snow into wind loaded features on west, north and east facing slopes at treeline and above. Storm slab avalanches could step down to deeper layers resulting in larger destructive avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 12th, 2022 4:00PM
