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Avalanche Forecast

Archived

Dec 4th, 2019–Dec 5th, 2019

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

Regions

Banff Yoho Kootenay.

Higher then forecasted snow fall amounts and strong winds have resulted in a heightened avalanche danger for the region.

Weather Forecast

Snow ending Wednesday with a short reprieve Thursday before the next system hits Friday which could bring an additional 20cm to the region. Temperatures will rapidly cool Thursday with a forecasted low of -20. This will be short lived, as the next wave of precipe moves in freezing levels could climb up to 1400m.

Snowpack Summary

20 to 30cm of new snow accompanied by moderate to strong SW winds have created fresh wind slabs on lees slopes at treeline and above. The midpack consists of 25-35 cm of facetted snow overtop of the Nov 8 crust. The lower snowpack consists of facets and depth hoar. Snowpack depths at treeline vary from 60-100 cm with up to 140 cm in lee areas

Avalanche Summary

Reactive wind slabs on alpine and treeline lee slopes are producing avalanches to size 2 in the region. Little evidence of these slabs stepping down to deeper instability has been observed, though with the current snowpack structure it is something to consider. We will likely find more evidence of an avalanches cycle Thursday as things clear up.

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.