Avalanche Forecast

Issued: Mar 7th, 2012 10:30AM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Another frontal system tracking inland from the NW Coast will bring unsettled conditions accompanied by light-moderate precipitation. Thursday: Mainly dry conditions with a mix of sun and cloud. Ridgetop winds moderate from the SW. Treeline temperatures near -3. Freezing levels 1500 m. Friday: Snow amounts moderate accumulating 15 cm. Ridgetop winds light-moderate from the SW. Freezing levels 1000 m, falling to valley bottom overnight. Saturday: Light snow amounts. Ridgetop winds L-M from the SW. Freezing levels near 1000 m.

Avalanche Summary

A widespread natural cycle occurred on Monday, operators reported numerous size 2-3.5 natural avalanches, starting in the alpine on all aspects and most elevations.. A minor natural cycle up to size 3 in the Alpine occurred Tuesday. Rider triggered slabs were also reported in the size 1-2 range, failing within storm snow instabilities. I suspect conditions will still remain touchy, and unpredictable. With more forecast snow, wind and warming the avalanche danger will elevate.

Snowpack Summary

The weekend past, 60-100 cm snow has fallen. Strong winds and fluctuating temperatures have created storm slabs and wind slabs on a widespread basis. Persistent weak layers (surface hoar, facets, crusts) buried in February are a concern at all elevations and could be triggered by storm slabs, wind slabs, or the additional load of a sled/skier. Avalanches may be unexpectedly large, and destructive. If the sun shines, watch for snowpack deterioration on solar aspects. Large cornices have formed, and may act as a potential trigger on slopes below. They could step down to the persistent weakness.

Problems

Storm Slabs

An icon showing Storm Slabs
New snow and fluctuating temperatures have formed storm slabs. These overlie the mid-February weak interface. Storm slabs that trigger this interface could create surprisingly large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 6

Wind Slabs

An icon showing Wind Slabs
Lots of snow available for transport, accompanied by strong winds have created wind slabs, even at treeline elevations. Large cornices may act as a potential trigger on slopes below.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Persistent Slabs

An icon showing Persistent Slabs
Persistent weaknesses exist in the 150 cm of the snowpack. Surprisingly large avalanches could be triggered naturally by storm snow loading, or by additional weight of a person/sled. Buried persistent weaknesses are tricky to predict.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 7

Valid until: Mar 8th, 2012 8:00AM