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Avalanche Forecast

Archived

Jan 11th, 2020–Jan 12th, 2020

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

Regions

Banff Yoho Kootenay.

Problems within the snowpack are complex and will likely persist for some time. There is great skiing, but now is the time for conservative decision making.

Weather Forecast

Mainly cloudy with isolated flurries of low density, fluffy snow. The temps will begin to drop and will range from -12 to -26, as the winds will shift Sunday morning and be light from the East. It will remain cold and mainly sunny until at least late next week.

Snowpack Summary

30-50 cm of snow since Jan 1 sits over a variety of surfaces including facets, surface hoar and sun crust. Stability tests throughout the region show 'sudden' results on this interface. Reactive wind slabs exist in alpine and some tree line locations. In most areas there is a well settled mid-pack over top of a weaker basal layer.

Avalanche Summary

Parks Canada responded to a size 2.5 skier triggered avalanche on the South flanks of Mt. Hector yesterday. Its suspected that the initially triggered wind slab stepped down to deeper layers.

Several naturals sz 2-3 were observed Thursday throughout the forecast region, some of which failed at the ground within the deep persistent layer.

Confidence

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.