Avalanche Forecast

Issued: Dec 8th, 2012 9:04AM

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

triley, Avalanche Canada

South Columbia.

If the Northwest winds pick up during the day and start to transport snow, then these danger ratings may be a little low for Sunday.

Summary

Confidence

Fair - Timing of incoming weather is uncertain on Sunday

Weather Forecast

Overnight and Sunday: Light NW winds and Alpine temperatures down to about -12.0 overnight. A warm front is forecast to move into the interior during the day that may cause an above freezing level to develop near treeline. NW winds are expected to increase during the day and become strong and gusty in the evening.Monday: Moderate westerly winds combined with temperatures of -7.0 in the alpine and very light precipitation.Tuesday:Strong SW winds in the morning as a cold front slides into the region. Expect 20-30 mm of precipitation falling as snow as the freezing level drops down to the valleys.

Avalanche Summary

Some very soft slabs were released with explosives control up to size 1.5 and heavy sluffing reported from ski cutting. There was one natural avalanche size 3.0 reported from the Southern Selkirks that likely released on the November rain crust.

Snowpack Summary

There has been 30-40 cms of new snow that fell with light winds in the past 48 hours. This brings the recent storm snow amount up to about 70-80 cms. 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.

Be cautious of sluffing in steep terrain.>On steep slopes, pull over periodically or cut into a new line to manage sluffing.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

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.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

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.>Choose regroup spots that are out of avalanche terrain.>

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

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

4 - 7

Valid until: Dec 9th, 2012 2:00PM