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Avalanche Forecast

Archived

Dec 1st, 2014–Dec 2nd, 2014

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

Regions

Little Yoho.

Avalanche control today is still yielding avalanches that have potential to capture, injure and/or bury human riders and climbers.  As the temperatures warm this week the risk will increase and conservative terrain choices are highly recommended. PJ

Weather Forecast

The cold spell of Arctic outflow is being displaced by a warmer air mass.  Light westerly winds are expected and temperatures will warm up significantly by the weekend so it will be a time to remain cautious and watch rising temperatures and solar warming and their strong influence on the stability of the snowpack.

Snowpack Summary

Recent storm snow has settled into a soft slab and has significant wind affect in open terrain at treeline and above. The lower half of the snowpack is a complex and poorly structured & comprised of the facets (Nov 24th) at the interface of the recent storm snow and a series of thin crusts (Nov 6th) and depth hoar at or slightly above the ground.

Avalanche Summary

Although natural avalanche activity has abated, Banff Visitor Safety performed avalanche control today on the Sunshine access road. Since the end of the storm there have a number of significant natural and explosive results indicating that there remains plenty of potential for human triggering of avalanches that can be large and destructive.

Confidence

Timing or intensity of solar radiation is uncertain on Wednesday

Problems

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.

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.