Avalanche Forecast

Issued: Dec 9th, 2011 9:30AM

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

Avalanche Canada ghelgeson, Avalanche Canada

Summary

Confidence

Fair - Due to variable snopack conditions

Weather Forecast

The ridge that has dominated the regions weather for the last week begins to break down on Saturday allowing a pacific front into the forecast area. The result will be high clouds and increased winds out of the W-SW clocking in between 65 and 80 km/h. Little or no precipitation is forecasted out of this system but the good news is that the door is once again open for storms to track across southern BC & AB. Temperatures on Saturday remain within seasonal norms: @ 1500m we can expect day time high's around -1 with overnight lows sinking to -13.

Avalanche Summary

There have been numerous avalanches both natural and human triggered from Size 2 - 3 in the adjacent forecast areas where avalanches have been failing near the ground on the crust/facet combo. If you have any observations from the field, please drop us an email: forecaster@avalanche.ca.

Snowpack Summary

We're off to a good start for early December with upper elevation snow depths that average a meter. It's been almost two weeks since our last significant storm and since that time the snowpack has suffered an unrelenting barrage of wind from around the compass rose. Wind exposed terrain is now a mixed bag of wind effected snow that varies from old hard windslabs to fresh small windslabs and everything in between. To travel safely at & above treeline you need to be able to recognize and avoid these potentially dangerous windslabs. This is the first part of the avalanche problem. Getting a little lower in the snowpack reveals some ugliness. A raincrust sits above large striated facets (sugar snow) on the ground. This is the classic Rockies house of cards setup that professionals throughout the region are concerned about. With numerous recent avalanches failing in this layer in the Rockies recently the chance of a large full depth avalanche remains a concern for backcountry travelers this weekend. Triggering an avalanche in this weak layer will result in a large & destructive avalanche that will likely be unsurvivable.This problem will not go away anytime soon. If I was putting together plans for the weekend I'd be combing through my terrain atlas (google earth) looking for slopes around treeline that are protected from wind. Once you're out in the field stay off of terrain features that are thin and weak. Rock's and/or tree's poking out of the snow are a good indication of thin weak snow. It's good practice to avoid terrain that is steep and rocky in general right now. Remember, it's only December and our snowpack needs some time to mature before we even start thinking about the bigger more committing terrain.

Problems

Wind Slabs

An icon showing Wind Slabs
High winds are likely to create touchy windslabs not only at ridge top, but further down onto slopes than you may expect. Watch for changing conditions throughout the day.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
With numerous recent avalanches failing on this layer in adjacent regions, the potential for large, destructive & likely unsurvivable full depth avalanches remains a concern for backcountry travelers this weekend.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Dec 10th, 2011 8:00AM