Avalanche Forecast

Issued: Mar 11th, 2012 10:59AM

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

Monday: Moderate snowfall arriving late in the day and continuing overnight - moderate to strong southerly winds - freezing level at 700m Tuesday: Continued moderate snowfall - moderate to strong westerly winds - freezing level at 500m Wednesday: Very light snowfall - light to moderate southwest winds - freezing level at 700m

Avalanche Summary

Avalanche observations were extremely limited on Saturday as most operators observed but 5% of their terrain. Having said that, a skier accidental avalanche occurred at 1900m on a south/southeast slope. The crown was between 30 and 80cm and it was suspected to have reacted on the early February interface. I expect ongoing wind/storm slab and persistent slab activity with forecast weather.

Snowpack Summary

Recent moderate snow accumulations and strong winds have been responsible for extensive wind transport at higher elevations, and recently developed hard and soft 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, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Storm Slabs

With ongoing moderate 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 12th, 2012 9:00AM