Avalanche Forecast

Issued: Dec 9th, 2011 9:03AM

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

Saturday: Expect high clouds with winds reaching 40-70 km/h from the southwest and temperatures climbing to -5. Sunday & Monday: The ridge rebuilds giving mostly clear skies and moderate westerly winds. Freezing levels could peak at 1200m on Monday.

Avalanche Summary

Reports of a few small explosive released avalanches in the Dogtooth.

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: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

The weak facetted layer near the ground may still be triggered by human activity. Areas with a lot of variability in the snow cover may be the most suspect. Triggering may occur from weak spots like rocks or clumps of small trees.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 10th, 2011 8:00AM