Avalanche Forecast

Issued: Dec 5th, 2011 9:14AM

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 triley, Avalanche Canada

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

A fast moving cold front is forecast to produce some light precipitation combined with strong winds from the southwest early Tuesday. The freezing level should drop to valley bottom overnight and remain below treeline on Tuesday. However, warm air is forecast to stay in the alpine during the day. Wednesday and Thursday should be cooler and drier with freezing levels rising to 1500 metres during the day.

Avalanche Summary

A few small size 1.0-1.5 avalanches have been reported. Some of these were natural releases in dry loose snow in steep terrain. One skier remote that triggered a slide in an adjacent bowl from a ridge top, and one skier accidental size 2.0 adjacent to a ski area in steep terrain on a south aspect in the alpine.

Snowpack Summary

Surface hoar has been forming over the last few clear and cold nights. Expect to find a sun-crust that has formed in the alpine on south through west aspects. I expect that the surface hoar will no longer be present on aspects that have developed the sun-crust. Wind slabs persist in the alpine and in large openings at treeline. The windslab has become less reactive to human triggers; however avalanches up to size 2.0 are still possible due to this problem. Some areas have a rain-crust below treeline from the 28th of November that has been buried by about 20 cms of snow. This rain-crust may be developing facets, and could become a layer of interest after it is buried by more of a load. There is still some concern associated with the early November buried surface hoar layer. This layer is buried down about 100-150 cms. Tests are showing that this layer is getting harder to release, and less likely to give clean and fast shears (Sudden Planar). If an avalanche does release on this layer, it is likely to be very large and destructive. Some areas also have a weak layer of facets at the base of the snowpack.

Problems

Wind Slabs

An icon showing Wind Slabs
Windslabs continue to be an issue in the alpine and in large openings at treeline. Reports suggest that triggering has become more stubborn.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Hard to trigger in most areas, but the consequences of triggering a slide on this layer may be a very large avalanche. Weaker thin spots around protruding rocks or clumps of small trees may be likely trigger locations.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Dec 6th, 2011 8:00AM