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Avalanche Forecast

Archived

Dec 22nd, 2012–Dec 23rd, 2012

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Coastal.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Mainly clear skies are expected for the forecast period. Expect temperature inversions with ridgetop temperatures of about -14.0. Winds should be mostly light and southeasterly with strong northeasterly outflows.

Avalanche Summary

Several size 2 avalanches were reported from the far north of the region. They failed at the ground on shallow, south-facing terrain. No other recent avalanches have been reported

Snowpack Summary

Light amounts of recent snow have been redistributed by strong winds into mainly stiff windslabs. This overlies older storm snow which has most likely settled and gained significant strength. In the mid snowpack you might find a buried surface hoar layer, reported to be 5 to 10mm in size. Last week it produced sudden snowpack test results down 60-80cm in the Shames backcountry, and may exist in other areas as well. In the far north there have been reports of faceted crystals in the top metre of the snowpack producing moderate to hard test results.At the base of the snowpack a faceted crust remains on the radar of avalanche professionals, particularly in the north of the region. It seems this problem is mostly confined to alpine areas and likely needs a large trigger and/or a shallow snowpack feature. Cornices are also large. Continued strong winds and cooling temperatures could make them especially heavy and brittle.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.