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Avalanche Forecast

Archived

Dec 18th, 2012–Dec 19th, 2012

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

Regions

Little Yoho.

Good skiing can be found in sheltered locations. Remember, a stable snowpack in December is different than a stable snowpack in April. Many thin/ weak spots still exist in alpine features. Hopefully the forecast of 5-10 cms on Thurs comes true!

Weather Forecast

Wed: Alpine temps in the -10 / -15 range. 1-2 cms snow, up to 5 cm N of Lake Louise overnight. Winds moderate from the W.

Thurs: Alpine temps -10/-15. 5-10cms new snow with higher values N of Lake Louise. Winds light from S/ SW.

Fri: Arctic air moves in.  Alpine temps -15/-20. Clearing skies. Winds light from SW.

Snowpack Summary

A few cm's of new snow overlies a slowly facetting snowpack. In the alpine, old windslabs exist and are visible as 'rippled' snow on the surface. These may be reactive to human triggering. The Nov. 6th crust is facetting out, and is now more of a facet layer than a crust in many places. This layer is giving hard to no results in compression tests.

Avalanche Summary

No new avalanches observed today by forecasters during a field trip in the Lake Louise ski hill backcountry.

Confidence

Forecast snowfall amounts are uncertain on Thursday

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.