Avalanche Forecast

Issued: Nov 24th, 2011 9:07AM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Moderate amounts of snowfall are forecast overnight. Friday conditions look dry with sunny periods. Freezing levels are expected to rise Friday afternoon up to 1000m then lower to valley bottom. Saturday afternoon freezing levels could rise to 2000m with snow to follow late in the afternoon or Saturday night. Sunday freezing levels could rise again 2000m accompanied by moderate to heavy snowfall.

Avalanche Summary

Several natural avalanches have been reported from the southern part of the region. These range in size anywhere from size 1.0-2.0 between 1900-2000m on southeast aspects. Avalanche control work also produced avalanches up to size 2.5 on southeast-southwest aspects between 1900-2100m. This information is from a portion of the region and avalanche activity may differ with size, aspect, and elevation around your local mountains.

Snowpack Summary

In upper elevations an average up to 70cm of new snow has fallen in the southern part of the region creating storm slab instabilities. This has been accompanied by moderate to strong winds from the southwest which are responsible for forming new wind slabs in the alpine and at treeline below ridgelines and terrain features. At treeline I suspect there to be some patchy areas of buried surface hoar and older raincrusts buried lower in the snowpack potentially up to a meter deep. With very limited observations from the field I suspect these layers (if existing) have or will reach their threshold and become reactive. I sense these layers will either clean themselves out, or start a healing process. Snowpack depths are likely in the 60-90cm range at about 1600m and up to 150cms at 2000m. This is a good time to sit out the storms and let the snowpack settle. There is a new post in the forecaster's blog, which is located at the bottom of the bulletin. The post entails "Post Storm Risk Management Strategy" written by Karl Klassen. Check it out, and let us know what you think.

Problems

Storm Slabs

An icon showing Storm Slabs
An average of 60cm of snow has fell over the past few days. This has created storm snow instabilities. Storm slabs are touchy, run far and can be destructive.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 4

Wind Slabs

An icon showing Wind Slabs
Strong winds will create new wind slabs on lee slopes and terrain features. These wind slabs may be found lower on the slope in unsuspected areas.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Nov 25th, 2011 8:00AM

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