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Archived

Avalanche Forecast

Dec 20th, 2012–Dec 21st, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Glacier.

Winds are forecast to rise today. Be cautious of wind slabs forming rapidly near ridge crests when these winds arrive.

Weather Forecast

A deep low off the coast of Vancouver Island with cool air at core brings cool temps and light impulses of precipitation for the next 4 days.

Snowpack Summary

At treeline and above, soft windslabs have formed due to 30-50k winds at ridgelines. Elsewhere, 40cm of loose storm snow overlies a well settled snowpack. The Nov28 surface hoar is down about 80cm but only in some locations. The early Nov crust is widespread and down about 1.5m. Tests on these layers indicate they would be hard to trigger.

Avalanche Summary

Yesterday No new avalanches were observed in Glacier National Park.

Confidence

Wind speed and direction is uncertain

Avalanche Problems

Wind Slabs

Strong winds early this week, combined with 40cm of storm snow have created touchy softslabs at treeline and alpine elevations that are easily triggerable on convex, unsupported features. Look for soft wind slabs at or near ridgelines.
Caution in lee and cross-loaded terrain near ridge crests.Be cautious of sluffing in steep terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3

Persistent Slabs

While the thick crust at the base of the snowpack has yet to be reactive, if it does produce an avalanche it will be very large. Cornice falls or other avalanches stepping down to this layer, or triggering from thin areas are possible.
Sluffs may trigger deeper instabilities.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4