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Avalanche Forecast

Archived

Dec 8th, 2012–Dec 9th, 2012

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

Regions

Little Yoho.

Winds Monday with a warm storm may bump the danger rating.  JBW

Weather Forecast

A warm Pacific push will bring cloudy skies and some precipitation for Sunday. On Monday the cold arctic air will move over the region and temperatures will drop. Winds are forecasted to increase to strong from the west on Sunday.

Snowpack Summary

Generally a well settled snowpack with some resistant planar shears related to the recent storm snow in the upper 40 cm. The Nov. Rain crust is approximately 30- 40 cm off the ground and is showing variable results. Good coverage and strength for early December.

Avalanche Summary

No new avalanches observed. On a flight today over the Wapta and Vermilion, several large size 2.5-3 full depth releases were observed that were approximately 3-4 days old. We suspect these failed on the Nov. crust.

Confidence

Wind speed and direction is uncertain 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.