Avalanche Forecast

Issued: Dec 9th, 2012 9:04AM

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

triley, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Overnight and Monday: Light precipitation and moderate Westerly winds overnight are expected to shift to the NW during the day and become gusty up to 60 km/hr. Freezing level should be about valley bottom, and alpine temperature about -7.0Tuesday:Expect the winds to shift to the NW and become gusty as the trailing cold front moves through the region bringing 15-20 mm of precipitation and freezing levels at about 800 metres. The alpine temperature should be about -8.0.Wednesday:There should be a bit of a dry spell during the day with a chance of very light precipitation and light NW winds. Alpine temperatures near -12.0

Avalanche Summary

Some very soft slabs were released with explosives control up to size 1.5 and heavy sluffing reported from ski cutting.

Snowpack Summary

There is widespread sluffing in the new snow in steep unsupported terrain, but no reports of slab avalanche failures in the storm snow. The late November surface hoar is now buried more than a metre deep and close to 150 cms in some of the snowier areas. This layer has mostly been found between 1700-2000 metres in elevation. There have not been any new reports of avalanches sliding on this layer. The early November rain crust is deeply buried. There was one report of a size 3.0 avalanche that released naturally on this layer in the southern Selkirks. I think we need to keep this problem on the front page through another storm cycle, and see how it reacts to more loading and rapid temperature changes.

Problems

Storm Slabs

Expect heavy sluffing in steep terrain, and some soft storm slabs on unsupported terrain features. Some new wind slabs may have formed on North thru East aspects at higher elevations.

The new snow will require several days to settle and stabilize.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

A variable surface hoar layer may be found buried down about one metre. This layer was buried in most parts of the region on Nov.28th. This may be found mostly at treeline between 1700-2100 metres.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Deep Persistent Slabs

The early November rain crust is deeply buried. This layer appears to be very drainage dependant, and there have only been a few avalanches reported across the region. Releases on this layer will be very large and destructive.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

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

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

4 - 7

Valid until: Dec 10th, 2012 2:00PM