Avalanche Forecast

Issued: Dec 19th, 2012 8:06AM

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

jon schleiss, Parks Canada

Glacier.

Rising winds are forcast to reach 70kph at ridge tops. This could cause rapid soft slab development. Use caution for soft wind slabs where slopes are exposed to the wind.

Summary

Weather Forecast

A large low in the gulf of Alaska is bringing cloudy and more stormy skies in from the South-West, flurries are forcast for today and tonight, and snow for Thursday. Amounts are predicted to be 2cm today, 5cm tonight, and 10 or more cm for thursday, but there is low confidence in the predicted amounts. Rising winds are forcast, SW 30 rising to S 70

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 avalanches were observed up to size 2.5, and were dry slabs running to 1/4 fan.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Wind Slabs

Strong winds early this week, combined with 40cm of storm snow have created touchy windslabs at treeline and alpine elevations that are easily triggerable on convex, unsupported features. Look for soft slabs at or near ridgelines.

Be cautious as you transition into wind affected terrain.Watch for terrain traps where small amounts of snow will acumulate into deep deposits.

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

Valid until: Dec 20th, 2012 8:00AM