Avalanche Forecast

Issued: Dec 29th, 2011 10:41AM

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

Avalanche Canada pgoddard, Avalanche Canada

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertainfor the entire period

Weather Forecast

Friday: Light snowfall, perhaps 10-15cm accumulation. Moderate westerlies.Saturday: Light snow. Freezing level near surface. Moderate westerlies. Sunday: Moderate precipitation. Freezing level rising to 1400m in the afternoon.

Avalanche Summary

Highways avalanche control produced numerous Size 2-3.5 slab avalanches. The largest of these failed at ground, up to 4m deep.

Snowpack Summary

Over the past week the northwest has been slammed by snow, strong to extreme winds, and fluctuating freezing levels. The week's tally is closing in on 200cm near Terrace, with areas to the north seeing a little less (Stewart up to 120cm). New snow has been blown around by strong south to southwest winds creating wind slabs on lee slopes and scoured windward slopes.In addition to the more obvious direct-action storm instabilities, local avalanche professionals have some other concerns: Surface hoar that formed during the winter solstice sits approximately 50-70cm below the surface. As well, the crust-facet combo (extends up to alpine elevations in the south and to 1000m in the north) from the early December dry-spell sits about 160cm below the surface and has not gone away. Any avalanches on this layer would be highly destructive and are probably waiting for the right load or trigger. Add the new observations of avalanches failing at ground and we have quite a package.

Problems

Wind Slabs

An icon showing Wind Slabs
Deep wind slabs are likely in exposed lee and cross-loaded terrain in the alpine and at treeline.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 7

Storm Slabs

An icon showing Storm Slabs
Storm slabs are growing in size and likelihood and may be triggered naturally or by the weight of a person.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 6

Persistent Slabs

An icon showing Persistent Slabs
There is a possibility of highly destructive avalanches where the deeply buried mid-December crust/facet layer persists.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 6

Valid until: Dec 30th, 2011 8:00AM

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