Avalanche Forecast

Issued: Dec 10th, 2011 8:53AM

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

mpeter, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Sunday: Expect clearing skies, with light winds and temperatures reaching -10. Monday: Mostly clear, with winds turning westerly but remaining light. Freezing levels could reach 1200m. Tuesday: Expect clouds to build and light flurries to begin late in the day under southwesterly winds.

Avalanche Summary

No new avalanches.

Snowpack Summary

Surface hoar continues to grow and the cold weather is penetrating into the upper snowpack giving near surface facetting. Steep south facing slopes may have developed a thin sun-crust. Windslabs continue to lurk in lee areas in the alpine and open treeline. Snow depths are quite variable through the region with 130-150cm in the alpine. There is still concern for triggering the weak basal facets/depth hoar, as these layers have shown sudden collapse results in stability test in shallow areas.

Problems

Wind Slabs

Stiff wind slabs in the alpine and open areas at treeline may be triggered by skiers and riders.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Persistent Slabs

The weak facetted layer near the ground may still be triggered by human activity with the common trigger points being convexities, rocks or clumps of small trees.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 11th, 2011 8:00AM