Avalanche Forecast

Issued: Dec 12th, 2021 4:00PM

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

Tim Haggarty,

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The bulk of the stormy weather has passed but unsettled conditions will remain with us for a few days. While we expect natural activity has dropped off, the potential for human triggering will linger. 

Summary

Weather Forecast

Winds have backed off to the moderate range and remain out of the SW Sunday evening and may diminish a bit further into Monday before returning to moderate into Tuesday. Temperatures have cooled to -10 Cat treeline and should remain there through Tuesday as a few cm of snow trickles in. 

Snowpack Summary

Up to 30 cm of storm snow since Saturday. 25-45 cm of snow now overlays the Dec 2 crust which is present up to 2100-2250 m. At treeline and above, strong to extreme W & SW winds have developed slabs in lee areas with extensive wind effect in exposed areas. The weak Nov 5 crust/facet interface is present near the ground.

Avalanche Summary

In the past 36 hrs there have been a few reports of skier triggered slabs at treeline including ski patrol and MIN reports. Additionally, explosive work at the ski hills produced several other slabs Beyond this there have been a few reports of natural avalanches generated out of the alpine described as audibles or visible as powder clouds.

Confidence

Due to the quality of field observations on Sunday

Problems

Loose Dry

An icon showing Loose Dry

20 to 30 cm of storm snow has developed ideal conditions for loose dry avalanches in steep terrain, including below treeline where the new snow sits on the slippery Dec 2 crust. Human triggered activity will remain likely until the new snow settles.

  • Be careful of loose dry sluffing in steep, confined or exposed terrain.
  • If triggered dry loose point releases can form deeper deposits in terrain traps.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 1.5

Wind Slabs

An icon showing Wind Slabs

Strong winds and new snow Friday though Saturday created fresh wind slabs in exposed terrain at treeline and above, and extensive wind effect in open areas. Human triggering of these slabs will remain likely in steep wind loaded terrain on Monday.

  • Watch for shooting cracks or stiffer feeling snow. Avoid areas that appear wind loaded.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

The new snow load may increase the likelihood of avalanches on the Nov 5 crust/basal facets for a few days. Steep shallow snowpack areas, cross loaded rocky terrain and areas exposed to large triggers such as cornices are the most concerning.

  • Be aware of the potential for full depth avalanches due to deeply buried weak layers.
  • Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 13th, 2021 4:00PM