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Avalanche Forecast

Archived

Dec 19th, 2022–Dec 20th, 2022

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

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

The extreme cold temperatures will continue for a few more days. The snowpack is weak and although natural activity has slowed, human triggering remains possible in all steep, skiable terrain. In some areas below treeline, the entire snowpack sluffs away underfoot and is unskiable.

Confidence

High

Avalanche Summary

Outflow (east) winds did some wind loading near Field as the cold air moved in and several small windslabs were reported on Mt. Stephen above the CPR tracks. These were small, but they ran a long way due to the facets.

Snowpack Summary

The snowpack is shallow and weak with a base of facets that won't support much weight. A 20-60 cm slab overlies this weak base and could easily be triggered in some locations. Loose, faceted sluffs are being triggered below treeline in some locations and any avalanches that do release will run further than expected with the cohesionless snow.

Weather Summary

The bitter cold Arctic ridge of high pressure will continue to dominate the weather for the next few days. Sunshine recorded -41 at their study plot today. Expect the same until Thursday, when the flow shifts back to SW and temps will rise back to more normal values.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.

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.