Avalanche Forecast
Issued: Dec 21st, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
ghelgeson,
Avalanche Canada
40 to 60 cm of snow now rests on a sketchy layer of surface hoar which has recently shown a propensity for connecting big pieces of terrain resulting in large avalanches, take a look at this example. It's time to seek out simple supported terrain that is not in avalanche paths.
Summary
Confidence
Low - Uncertainty is due to the limited number of field observations. Uncertainty is due to extremely variable snowpack conditions reported through the region.
Weather Forecast
Looks like we’re moving into a bit of a clearing trend this week.
MONDAY NIGHT: Freezing level at valley bottom, moderate NE wind, trace of snow expected.
TUESDAY: Scattered cloud cover, freezing level at valley bottom, light northerly wind, no significant precipitation expected.
WEDNESDAY: Scattered cloud cover, freezing level at valley bottom, light southwest wind, no new snow expected.
THURSDAY: Scattered cloud cover, freezing level at valley bottom with potential for a light alpine temperature inversion, light southerly wind, no new snow expected.
Avalanche Summary
There was a smattering of reported natural and human triggered avalanches on Saturday throughout the region with humbling photos of large avalanches. The MIN posts from the weekend really tell the story, you can view them all here. This observation from Sunday on a north facing slope looks to be failing on the mid December surface hoar.
Snowpack Summary
A steady stream of storms has resulted in 30 to 65 cm of light density new snow across the region with areas to the east around Blue River getting the larger amounts. Southwest winds have built slabs in lee features at upper elevations.
A spooky and active weak layer is now down 40 to 70 cm below the surface. In some areas it's a crust, in others it's surface hoar, and it may be surface hoar on top of a crust in some zones. The bond at this interface is poor and avalanches have recently failed on this interface throughout the region.Â
Near the base of the snowpack is a crust that was buried in early November. This crust likely has weak facets associated with it. There have been no recent avalanches reported on this layer, though it may be possible to trigger from shallow, rocky terrain.
Terrain and Travel
- Avoid freshly wind loaded terrain features.
- Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
- Use careful route-finding and stick to moderate slope angles with low consequences.
Problems
Storm Slabs
These storm slabs will likely become less sensitive to human triggering as we move into clear weather this week, but they remain a player, especially in wind loaded terrain features.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
This layer was touchy through the weekend producing large to very large avalanches. The slab rests on a persistent weak layer which has the capacity to propagate avalanches across terrain features. Wind exposed features are expected to be particularly problematic.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 22nd, 2020 4:00PM
