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Archived

Avalanche Forecast

Dec 21st, 2011–Dec 22nd, 2011
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Northwest Inland.

Confidence

Fair - Track of incoming weather is uncertain

Weather Forecast

Thursday: Strong ridgetop winds from the SW with snow amounts near 10cms. Treeline temperatures near -5. Friday-Saturday: Freezing levels may rise to 1100m. Mix of snow and rain at lower elevations. Snow amounts near 12cms. Ridgetop winds strong from the west.

Avalanche Summary

No new avalanche activity has been reported. Any information (professional or recreational) from the field is highly appreciated. Please send your observations to [email protected].

Snowpack Summary

Early in the week the region received up to 20cms of new snow accompanied by strong southwest winds. Storm snow and wind slabs are forming. There could be up to 50cms total from last week's snowfall and the current snowfall loading the weak layers in the upper part of the snowpack. These weak layers are the December 12th surface hoar/crust/facet combo. What is the tipping point of this weak interface? In areas where this interface has reached its threshold avalanches have occurred. If they have yet to happen naturally, I suspect they are very touchy and will react to a rider trigger. Observations suggest there is faceting above and below the crust. The crust being a result from rising freezing levels, then the early December dry spell. This crust is widespread and is lingering in most start zones up to 2000m. In short, the upper snowpack is variable and showing easy shears in test results. The midpack seems to be well settled and strong.

Avalanche Problems

Persistent Slabs

Reactive storm slabs have now formed at all elevations. Especially where the mid-December buried surface hoar/crust/facet layers exist.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Wind Slabs

Wind slabs have developed on lee and cross-loaded terrain in the alpine and at treeline. Rider triggered wind slabs are likely.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3