Avalanche Forecast

Issued: Dec 18th, 2011 9:06AM

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

Avalanche Canada jlammers, Avalanche Canada

Summary

Confidence

Poor - Intensity of incoming weather is uncertain on Monday

Weather Forecast

Snowfall amounts for monday are highly uncertain, but some models are calling for 20-30cm on the west side of the region. Expect moderate to strong wind values and freezing levels between 500-1000m.On tuesday expect light to moderate snowfall with light westerly winds in the morning with clearing late in the day. Forecast freezing levels at about 300m.Clearing is forecast for wednesday with light to moderate southwest winds and freezing levels at surface.

Avalanche Summary

On saturday evidence of a size 2 natural avalanche cycle was reported in the Hankin area. There was also human triggering to size 2.5 in the same area. It is thought that these slides are releasing on the crust/surface hoar/facet interface. Forecast weather is uncertain for monday. If precip values are on the high side, expect another spike in natural avalanche activity for the region.Any information (professional or recreational) from the field is highly appreciated. Please send your observations to forecaster@avalanche.ca.

Snowpack Summary

Over the past week the region has received approximately 40cm of snow that now sits on a variety of weak snow surfaces (melt-freeze crust, surface hoar above the crust and facetted snow below the crust) that are a result of rain and then the early December dry spell. This crust is widespread and is lingering in most start zones up to 2000m. The recent winds in the alpine seem to have destroyed the surface hoar in exposed areas in the alpine possibly eliminating that issue, but creating a wind slab problem. In short, the upper snowpack is variable and showing easy shears in test results. A cautious approach is required as monday's forecast calls for new slabs to continue to form over the buried weak layers. The midpack seems to be well settled and strong.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs have developed on lee and cross-loaded terrain in the alpine and at treeline. They are reactive and destructive.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Storm Slabs

An icon showing Storm Slabs
Reactive storm slabs have now formed in the alpine and at treeline.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Dec 19th, 2011 8:00AM

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