Avalanche Forecast

Issued: Mar 10th, 2012 9:58AM

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.

Avalanche Canada jlammers, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertain on Sunday

Weather Forecast

Sunday: 15-25cm of snow - moderate southwest winds - freezing level at 1100m Monday: light snowfall - moderate to strong southwest winds - freezing level at 800m Tuesday: very light snowfall - moderate southwest winds - freezing level at surface. Confidence is fair in snowfall amounts forecast for Sunday

Avalanche Summary

Avalanche observations were extremely limited on Thursday and Friday; however, natural avalanches to size 2.5 were observed on Wednesday. On the same day, it was suspected that cornice fall was the trigger for a size 3.5 slab on a west facing alpine feature. Several skier-triggered size 1.5 avalanches within the recent storm snow were also reported in the region. Expect ongoing storm slab avalanches as well as deep persistent slab avalanches throughout the forecast period, especially with weather forecast for Sunday.

Snowpack Summary

Recent moderate snow accumulations and strong winds have created 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

An icon showing Persistent Slabs
Persistent weaknesses are buried up to 150cm below the surface. Surprisingly large avalanches could be triggered naturally by the additional load of snow forecast for Sunday, or by the additional weight of a person/sled.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

3 - 7

Wind Slabs

An icon showing Wind Slabs
New snow and moderate winds will continue to create 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 - 4

Storm Slabs

An icon showing Storm Slabs
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

Possible - Likely

Expected Size

2 - 6

Valid until: Mar 11th, 2012 9:00AM