Avalanche Forecast

Issued: Dec 8th, 2011 9:16AM

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

Avalanche Canada jlammers, Avalanche Canada

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Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

A ridge of high pressure will persist through friday bringing clear skies, seasonal temperatures and light northwesterly winds. On saturday, the ridge should erode as a cold front is expected to bring increased cloud, very light flurries, light westerly winds and slight warming.On sunday the ridge should rebuild with clear skies, cooler temps and light northwesterly winds.

Avalanche Summary

There are no new observations of avalanches from this region. It has been about a week since we have had new snow in this area. The avalanche problems have been decreasing in likelihood, and the expected size has also been decreasing. I have decreased the avalanche danger at treeline to LOW, and have kept the danger rating in the alpine at MODERATE due to the likelihood of releasing an old windslab avalanche. There is still a chance of triggering a very large avalanche from a weak thin spot in areas with variable snowpack depth.

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 should be settling and becoming a bit more stubborn to trigger. Hard slabs in the alpine may propagate into large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Probability of triggering has decreased. Where it still exists, this layer may be capable of producing highly destructive, full depth avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Dec 9th, 2011 8:00AM