Avalanche Forecast

Issued: Dec 24th, 2011 9:07AM

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

Avalanche Canada jlammers, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertainfor the entire period

Weather Forecast

Sunday: Trace amounts of snow - Freezing level at 500m - moderate westerly windsMonday: 10-15cm of snow - Freezing level at 400m - moderate to strong southwest windsTuesday: light to moderate snowfall - Freezing level at surface - light to moderate southwest winds

Avalanche Summary

No new avalanches have been reported. 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 Hankin/ Hudson Bay Mtn area received up to 30cms of new snow accompanied by strong southwest winds. Storm slabs and wind slabs have formed. There is now around 55cms of snow sitting on a surface hoar/crust/facet combo which is the result of the early December dry spell. This crust is widespread and exists in most start zones up to 2000m. Facets can reportedly be found above or below the crust. Prior to being buried, the surface hoar was destroyed by high winds in the alpine, but still coexists with the crust at treeline and below. What is the tipping point of this weak interface? In areas where this interface has reached its threshold, natural and human triggered avalanches up to size 2.5 have occurred. If they have yet to happen, I suspect they are gaining some strength but would still react to a rider trigger, especially in steeper, unsupported terrain features. In short, the upper snowpack is variable and deserves caution. It will also see increased load with forecast wind and snow.Beneath this the midpack is well settled and strong.The base sits at about 115cm at treeline and about 135cm in the alpine.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Persistent slabs have now formed at all elevations where the mid December buried surface hoar/crust/facet layers exist. Reactivity has probably decreased somewhat, but the consequence of an avalanche remains high.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Wind Slabs

An icon showing Wind Slabs
Wind slabs have developed on lee and cross-loaded terrain in the alpine and at treeline. Rider triggered wind slabs are possible.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Dec 25th, 2011 8:00AM

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