Avalanche Forecast

Issued: Dec 23rd, 2011 9:04AM

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

mpeter, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Due to variable snopack conditions

Weather Forecast

Saturday: Mostly cloudy with a chance of flurries. Expect moderate southwest winds and temperatures reaching -3. Due to the nature of the weather pattern, expect more precipitation on the western half of the region and on west facing slopes. Sunday: A weak cold front passes through the region giving unsettled skies with a chance of flurries. Continued southwest winds and freezing levels reaching 1100m. Monday: Expect clearing conditions under southwest winds and freezing levels to 1100m.

Avalanche Summary

No new avalanches.

Snowpack Summary

There is about 20-30cm of recent storm snow sitting over the December 12 interface of surface hoar and facets. This new snow has been deposited into soft slabs on lee features in open terrain by the consistent winds. The interface between the new snow and older surfaces is gaining strength, but still remains within the threshold of human triggering where there is sufficient load/slab properties. Some areas have a sun crust in the alpine on steep south and west aspects. Lower in the snowpack, the mid-layers are well-consolidated and strong. Near the base of the snowpack there are a few layers that have the potential to wake up with a really big storm or very heavy loads. These include a surface hoar layer from early November, a crust/facet combo from October and the interface on steep glaciated terrain with snow that did not melt over the summer.

Problems

Wind Slabs

Shifting winds have set up this problem on a variety of aspects, particularly north through south east.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

Slab avalanches continue to be a concern on the December surface hoar/facet interface in northern parts of this region.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 24th, 2011 8:00AM