Avalanche Forecast

Issued: Dec 22nd, 2011 8:57AM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertainfor the entire period

Weather Forecast

Friday: Ridgetop winds 40-75km/hr. Snow amounts 5-10cms. Treeline temperatures near -5. A strong southwesterly flow with embedded disturbances will spread 5-10cms on Saturday and up to 15cms on Sunday. Freezing levels will rise to 1300m over the weekend then drop to 1000m by Monday morning. Snow amounts will be less in the eastern parts of the region.

Avalanche Summary

No new observations reported since Wednesday. You need to be very aware and make observations while you travel in avalanche terrain at all elevations. Reports of rider triggered avalanches occurred Monday-Wednesday. Most of this avalanche activity has occurred on the early December surface hoar/facet/crust layer.

Snowpack Summary

The Cariboos received up to 50cm of new storm snow over the past few days. Strong southwest winds and warm temperatures have created wind slabs on North through East aspects in the alpine, and at treeline. Storm slabs are between 50-80cms and sit on the mid December surface hoar/facet/crust interface. This interface is where the avalanche problems exist. The snow load is fatter in the northern ranges than in the southern and eastern ranges. The storm slabs are between 50-80cms and sit on the mid December surface hoar/facet/crust interface. This weak layer has been very active; especially to rider triggers. Reports indicate that this weak layer has failed in some locations naturally, but where avalanches haven't occurred I suspect it's ripe and just waiting for a trigger. This is my main concern for the holiday weekend. Also buried in the snowpack exists a sun crust in the alpine on steep south and west aspects. Additionally there is a rain crust that is buried between 40-55cms in some areas that reaches up to about 2200 metres. The mid-pack is generally strong and well settled. Observers are still able to find the early November surface hoar layer that sits around 120-150cms down. This layer has not been reactive during the recent loading after our 2 week dry spell. It may be time to put this layer to bed.

Problems

Persistent Slabs

An icon showing Persistent Slabs
The recent storm snow is settling into a cohesive slab above the early December buried surface hoar/facet interface. This weakness is touchy to rider triggers and may produce wide propagations in protected terrain features.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Wind Slabs

An icon showing Wind Slabs
Expect wind slab development on lee and cross-loaded features. Also anticipate loading lower on the slope with high winds.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Valid until: Dec 23rd, 2011 8:00AM