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Avalanche Forecast

Archived

Dec 19th, 2012–Dec 20th, 2012

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

Regions

Little Yoho.

Increased winds are creating thin new slabs in the alpine and at treeline. If the forecasted winds arrive, the hazard will rise. Otherwise, great skiing on a generally stable snowpack.

Weather Forecast

Moderate confidence in the forecasted snowfall amounts.

Thurs: Alpine temps -10/-15. 5-10 cms snow with higher values N of Lake Louise.  Alpine winds moderate to strong from the SW.

Fri: Alpine temps -10/-15. Clear. Alpine winds light from the S.

Sat: Alpine temps -15/-20. 5 cms of new snow. Alpine winds light from the E.

Snowpack Summary

5-15 cms of new snow overlies a well settled midpack. At ridgetop elevations, moderate S/SW winds are forming thin soft slabs in the immediate lee on N through E. 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 Sunshine ski hill backcountry.

Confidence

Wind speed and direction is 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.