Avalanche Forecast

Issued: Nov 30th, 2013 8:22AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada rbuhler, Avalanche Canada

New snowfall amounts are uncertain for Sunday. If more than 20 cm of new snow falls in your area, the local avalanche danger may be HIGH.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Sunday

Weather Forecast

Two weather systems will collide today creating storm conditions over the interior regions. A cold arctic front will interact with moist air from the pacific creating heavy snowfall and moderate to strong winds.Sunday: Heavy snowfall, moderate to strong alpine winds from the SW, freezing levels around 500mMonday: Light snowfall, moderate to strong alpine winds from the NE, temperatures becoming unseasonably coldTuesday: Dry, cold, mostly sunny, moderate alpine winds from the NE

Avalanche Summary

No recent avalanches have been reported but incoming field data is still very limited.

Snowpack Summary

Highly variable snowpack conditions are being reported but typically 1m of old, well-settled snow lies below the new storm snow. New storm slabs are forming on over a variety of old snow surfaces including (1) winds slabs and wind scoured areas in the alpine and exposed areas at treeline, (2) sun crusts on steep south facing slopes, and (3) surface hoar in sheltered areas around treeline elevation and below. There are still two layers of concern within the mid/lower snowpack: the early November surface hoar is down roughly half way (50-60cm) and the October rain crust is near the ground. While these layers have recently become dormant, the weight of the new storm snow may cause these layers to reactivate in isolated areas causing large, destructive avalanches. The October crust can be found in the alpine on north aspects (likely east and west as well). The early November surface hoar appears to be spotty and drainage specific.

Problems

Storm Slabs

An icon showing Storm Slabs
New storm snow may be sitting on the late November surface hoar/sun crust. Stiffer wind slabs are also expected on leeward slopes and may result in larger avalanches.
Use extra caution in lee areas in the alpine. Recent wind loading has created wind slabs.>The new snow will require several days to settle and stabilize where it overlies a weak layer.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
The October rain crust and the early November surface hoar have been dormant for several days but have the potential to reactivate with the weight of the new snow. Smaller storm avalanches may have the potential to step down to one of these layers.
Caution around convexities and large, unsupported slopes.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Dec 1st, 2013 2:00PM

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