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Avalanche Forecast

Archived

Dec 6th, 2021–Dec 7th, 2021

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Little Yoho.

The current avalanche hazard fits the definition of Moderate, however our main concern is with full depth avalanches failing on the basal facets which could result in high consequences if triggered. Thinner snowpack areas seem the most problematic.

Weather Forecast

Expect slightly warmer temperatures tonight and Tuesday with highs around -7C, isolated flurries, and moderate W ridge winds. No significant snow amounts for tomorrow, maybe up to 10 cm for Wednesday.  See Avalanche Canada weather forecast for more details.

Snowpack Summary

Last weeks storms brought up to a meter of settled snow at higher elevations with wind effect in open areas. Periods of rain as high as 2200 m formed a crust which is down 5-30 cm depending on elevation. The lingering Nov 15 interface is down 50-100+ cm and the Nov 5 crust/facet layer is found near the ground. 120-200 cm of snow at treeline.

Avalanche Summary

No new natural avalanches were observed today. One significant skier accidental size 3 with a sympathetic size 2+ avalanche were triggered on Lipalian Mtn and failed on the basal facets. This thinner snowpack area with variable snow depths, cross loading by the wind and steep rolls is the type of terrain we are most concerned with at this time.

Confidence

Due to the number and quality of field observations

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.