Avalanche Forecast

Issued: Dec 19th, 2011 9:53AM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertain on Thursday

Weather Forecast

Heavy snow amounts expected through Tuesday easing off in the afternoon. Strong southwest ridgetop winds switching from the northwest later in the day. Freezing levels may rise to 1000m then falling to valley bottom overnight. Wednesday brings mainly dry conditions with few flurries and winds from the southwest. Thursday and Friday moderate -heavy amounts of snow is expected.

Avalanche Summary

Numerous size 2 naturals were observed in steep terrain on all aspects in the Bear Pass area on saturday. Near Shames recent size 2 naturals were observed as were significant whumphing and cracking.

Snowpack Summary

The forecast region continues to get slammed by snow, wind and fluctuating freezing levels. The southern part of the region has received a meter + of new snow over the past week (Kasiks, Terrace areas). Locations to the north are seeing a lot of weather with a little less snow accumulations. Storm slabs are continuing to form at all elevations throughout the forecast region. This new snow has been blown around by strong southwest winds creating new wind slabs on lee slopes. Buried beneath the new snow sits a variety of weak snow surfaces (melt-freeze crust, surface hoar above the crust and facetted snow below the crust) that are a result of rain and then the early December dry spell. This crust is up to 20cm in thickness and extends up to alpine elevations in the south, and around 1000m in the north. The surface hoar growing on the crust was sized up to 10mm. I suspect the surface hoar has been cleaned out in most locations during the past storm cycles. I'm sure it still exists in some locations; especially where snowfall amounts have been less. With more forecast snow and wind these layers may reach their threshold. If they have, you can expect re-loading to occur on the bed surfaces.The mid and lower snowpack continue to be well settled and strong.

Problems

Wind Slabs

An icon showing Wind Slabs
Strong winds will form large wind slabs on cross-loaded and lee slopes. They will be touchy and destructive in many parts of the region.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 5

Storm Slabs

An icon showing Storm Slabs
Heavy snowfall amounts will create storm slabs at all elevations. They will be touchy and destructive; especially in areas with a weak buried surface hoar/crust/facet interface. Storm slabs can run fast and be destructive.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 5

Valid until: Dec 20th, 2011 8:00AM

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