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Avalanche Forecast

Archived

Dec 10th, 2012–Dec 11th, 2012

Alpine
Natural avalanches possible, human triggered probable.
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

Little Yoho.

Strong wind from the NW have created wind slabs in alpine lee areas. Human triggering is possible in these areas.

Weather Forecast

Subsiding wind, warming temperatures and a clearing trend will contribute to decreasing the danger rating from considerable to moderate over the next few days.

Snowpack Summary

Wind slabs of varying thickness have been developing on NE through SE aspects due to the moderate to strong wind. These wind slabs sit over top of a well settled mid pack and the Nov 6 rain crust. The Nov 6th crusts lies approximately 30cm from the ground.

Avalanche Summary

One size two avalanche was observed high on Bourgeau 8, above the Bourgeau Left ice climb. It is suspected to be a recently developed wind slab from todays wind event. No other avalanches were observed or reported. Photo of avalanche in Bourgeau 8.

Confidence

Wind effect is extremely variable on Monday

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.