Avalanche Forecast
Issued: Dec 22nd, 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.
MBender,
Avalanche Canada
Heavy snowfall over the past several days has increased the load on a variety of buried weak layers. Now is the time to adopt a conservative approach to terrain selection as the snowpack adjusts to this new load.
Summary
Confidence
Weather Forecast
TUESDAY NIGHT: Broken cloud cover, moderate northwest wind, alpine temperature near -12 C.
WEDNESDAY: Mainly clear skies, light variable wind, alpine temperature near -8 C.
THURSDAY: Mainly clear skies, light to moderate southwest to west wind, alpine temperature near -3 with potential for a light alpine temperature inversion.
FRIDAY: Mix of sun and cloud, light to moderate southwest to west wind, alpine temperature near -4, freezing level 1200 m.
Avalanche Summary
With heavy snowfall Monday into the night, I suspect there was widespread avalanche activity through the night into Tuesday. Check out this MIN report from Tuesday afternoon. During the day on Monday reports indicate a few explosives controlled size 1-2 storm slab avalanches in the north of the region.
On Sunday, avalanches to size 2 failed naturally and were sensitive to avalanche control measures. Reported avalanche activity primarily came from northeast, north and northwest facing features at and above treeline. This MIN highlights that activity nicely.
On Friday and Saturday the buried surface hoar continued to show it's stuff making for touchy avalanche conditions which produced slabs to size 1.5, check out this great MIN report from the north of the region Saturday. Natural wind slabs and cornice failures were reported on alpine features in the central portion of the region to size 1.5.
In the south of the region the snowpack is thin and there have been reports of whumphing at ridgetop. Check out all of the MIN reports for the region here
Snowpack Summary
30 to 75 cm of storm snow has fallen recently with the deepest amounts being found in the north around Golden. Southwest winds have built slabs in lee features at upper elevations, reactive cornices have grown too.
Below the storm snow, the snowpack is a bit of a junk show. The early December surface hoar is down 30 to 80 cm below the surface now. On Saturday, before the big storm, it was sensitive to remote triggering which is well illustrated in this MIN post from the Golden area.
Below, or near the surface hoar you may encounter a crust. This crust can be bound as high as 2400 m in the south of the region and 1800 m in the north.
The lower snowpack is characterized by more crusts, the most notable is a rain crust from early November that is 50 to 130 cm deep. This crust is sitting near the base of the snowpack, surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers or in a step-down from a smaller avalanche in shallow, rocky areas.
Terrain and Travel
- Uncertainty is best managed through conservative terrain choices at this time.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Remote triggering is a concern, watch out for adjacent and overhead slopes.
Problems
Storm Slabs
20 to 35 cm of new snow fell Monday night combined with moderate northerly wind. Watch for the formation of fresh sensitive slabs in the new snow that will likely continue to be sensitive to human triggering.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A buried layer of surface hoar is now primed for human triggering. 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 volatile.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 23rd, 2020 4:00PM
