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Avalanche Forecast

Archived

Dec 2nd, 2021–Dec 3rd, 2021

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 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.

Cooler temperatures are on the way, which should improve the danger over the next few days. However, users can still trigger large, destructive avalanches.

Weather Forecast

Thursday AM, alpine temperatures will decrease to -15C and valley bottom temperatures at -7 to -10C. Temperatures should stay below freezing, with moderate alpine winds diminishing over the day. No snow expected Thursday.

Snowpack Summary

Wednesday's storm started as rain to 2400m for most of the day, saturating the snowpack, and turned to snow Early Thursday AM. Anywhere from 30-100cm was deposited from this storm in the alpine with high settlement from warm temperatures. A midpack Nov.15 crust is found below 2100m, and the Nov. 5 crust/facet layer exists near the ground.

Avalanche Summary

Wednesday saw many natural avalanches to size 3.5, and Thursday produced sporadic results. Some targets produced minimal results, but some results were 40-100cm deep storm slabs, with some stepping down to the basal crust/facets. A few crowns where it stepped down were 200cm deep.

Confidence

Due to the number and quality of field observations on Thursday

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.