Avalanche Forecast

Issued: Mar 12th, 2012 10:37AM

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

jlammers, Avalanche Canada

Cariboos.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Tuesday: light snowfall - moderate west winds - freezing level at surface Wednesday: Very light snowfall - moderate southwest winds - freezing level at 600m Thursday: moderate to heavy snowfall - strong southwest winds - freezing level at 1100m

Avalanche Summary

Recent avalanche observations have been extremely limited . Having said that, a few recently formed storm slab avalanches (size 1.5-2) were ski cut on north aspects at treeline and below. In the alpine a few natural avalanches to size 2.5 also occurred. I expect ongoing wind/storm slab and persistent slab activity with forecast weather.

Snowpack Summary

Recent snow accumulations have been variable throughout the region, but mostly moderate daily accumulations and strong winds have been responsible for extensive wind transport at higher elevations, and recently developed wind slabs now exist at treeline and in the alpine. In the mid snowpack lies the mid-February surface hoar. Buried over a metre down, this surface hoar may exist in combination with crusts or facets. These persistent weaknesses have remained reactive all week and are an ongoing concern at all elevations as avalanches may be unexpectedly large and destructive. Large cornices have formed and could also act as a trigger on the slope below.

Problems

Persistent Slabs

Persistent weaknesses are buried up to 150cm below the surface. Surprisingly large avalanches could be triggered naturally by the weight of additional snowfall, or by the energy of a person/sled.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

3 - 7

Wind Slabs

New snow and moderate to strong winds will continue to form reactive wind slabs on lee features. Large cornices may also act as a trigger on slopes below.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Storm Slabs

With ongoing snowfall, storm slabs are continuing to form on all aspects and elevations. Surprisingly large, destructive avalanches will occur if storm slabs step-down to a persistent weak layer buried below.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 5

Valid until: Mar 13th, 2012 9:00AM