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Avalanche Forecast

Archived

Dec 26th, 2014–Dec 27th, 2014

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

Regions

Little Yoho.

The skiing has improved due to recent snow, however there is a poor bond at the storm snow interface which will persist for some time and the snowpack is weak. Avoid larger features and steeper terrain. Good skiing can be found on lower angled slopes

Weather Forecast

A few flurries overnight then a clearing and cooling trend starts on Saturday. Clear skies, light NE winds and cold temperatures are forecast for Sunday and Monday.

Snowpack Summary

Recent winds have created small wind slabs in the alpine which sit over the Dec 18 layer of crust, facets and/or surface hoar depending on the location. A poor bond exists at this interface. At the base of the snowpack weak crusts and facets exist which are still a concern.

Avalanche Summary

"Speed Run" at Lake Louise ran naturally as a size 2 on December 26th following some moderate wind transport overnight. A couple other natural avalanches up to size 2 were also observed. Following the storm last week avalanches up to size 2.5 were observed with propagations up to 200 m, and occasionally stepping down to the basal facets/crusts.

Confidence

Due to the number of field observations

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.