Avalanche Forecast

Issued: Dec 17th, 2011 8:45AM

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

triley, Avalanche Canada

Purcells.

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Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

A cold front is expected to move through the interior on Saturday night. This trailing cold front will follow in the wake of the warm air that we saw on Saturday and is forecast to bring another 10 cm by Sunday morning to the North and West regions of the Monashees and Cariboos. Less snow is forecast for the South and East areas of the Selkirks and Purcells. Freezing levels are expected to fall back to valley bottoms as cold air and moderate to strong Northwest winds move over the interior. Sunday is expected to be mostly dry but probably still overcast. Clearer and colder weather should be across the interior on Monday. The next Pacific system is expected to start moving in from the coast on Tuesday. It is a little early to determine intensity and timing for the next system.

Avalanche Summary

No new avalanches reported.

Snowpack Summary

Problems

Wind Slabs

This problem is changing from old wind slab on a non-persistent layer, to new soft wind slab on a recently buried surface hoar and/or crust layer. Remember that old wind slabs exist, and that new more touchy wind slabs are developing.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Loose Dry

As the new storm snow builds up above the recent surface hoar we could see sluffs that entrain enough snow to bury or injure a person. When the storm snow settles or is wind blown into a slab it may propagate wider avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

Highly variable snow depths make this very difficult to predict. Weaker thin spots on convexities or around protruding rocks/clumps of small trees may be likely trigger locations for deeper avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 5

Valid until: Dec 18th, 2011 8:00AM