Avalanche Forecast

Issued: Dec 22nd, 2020 3:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is considerable. Known problems include Wind Slabs and Deep Persistent Slabs.

Avalanche Canada JMackenzie, Avalanche Canada

Email

Pull in the reins! Lots of new snow, but hazard is high. Human triggering of avalanches is very likely.

Summary

Confidence

Moderate -

Weather Forecast

Wednesday should be mainly sunny with a brisk -20c to start the day. Temperatures should rise to near -11c with winds out of the north in the light to moderate range. No new snow is expected.

Avalanche Summary

Observations have been somewhat limited by poor visibility, but an avalanche cycle is occurring. Numerous slabs and loose dry avalanches up to size 2.5 have occurred in the past 24 hours. These are occurring at all elevations and on all aspects.

Snowpack Summary

40 to 50cm of snow fell in a very short period of time, which has overloaded the snowpack. Winds were strong out of the north during the storm, so expect widespread wind slabs at Treeline and above. The Dec 8th layer of surface hoar/crust/facets remains on the radar, especially with this new load. The Nov rain crust is now deeply buried in the snowpack, and while it hasn't been reactive recently, it could easily wake up with the new snow load. Field observations were very limited today, and forecasters will be going out with eyes wide open on their next field day - the snowpack has experienced significant change!

Terrain and Travel

  • Avoid steep convex slopes.
  • Back off steep and aggressive lines, stick to simple terrain.
  • Make conservative terrain choices and avoid overhead hazard.
  • Be cautious of sluffing.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.

Problems

Wind Slabs

An icon showing Wind Slabs

Freshly formed surface wind slabs could be as deep as 60-80cm and will be very sensitive to human triggering. Also watch for previously formed (now buried) wind slabs with failure planes deeper in the snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1.5 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

A lot of new load has been added to the snowpack. The deep weak layer of the Nov crust may become active.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3.5

Valid until: Dec 23rd, 2020 3:00PM