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Avalanche Forecast

Archived

Nov 25th, 2019–Nov 26th, 2019

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

Regions

Banff Yoho Kootenay.

The main avalanche concern for the next few days is a lingering wind slabs formed over the weekend. Natural avalanche activity on this problem has subsided, but the likelihood of human triggered wind slab is still possible.

Weather Forecast

A predominant North West flow has moved into the forecast region. Expect clear and calm conditions for Tuesday, Wednesday with temperatures dropping down to below -20 for the daytime lows. Temperatures will gradual warm up later in the week.

Snowpack Summary

10-20 cm of new snow with strong W winds have formed wind slabs at ridge tops and in open alpine areas over the weekend. The Nov 8 crust is down 20-30 cm and is present up to ~2400 m. The lower snowpack is a mix of facets and the Oct crusts. Snowpack depths at treeline range from 60-90 cm with up to 140 cm in lee areas.

Avalanche Summary

Wind slabs formed on the weekend continue to produce avalanches to size 1.5 at alpine elevations. Reports from local ski resorts have noted that the wind slab problem has still been reactive to skier triggering and explosive control .

Confidence

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.