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Avalanche Forecast

Archived

Nov 17th, 2019–Nov 18th, 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, human triggered possible.
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.

Fresh wind loading and mild temperatures on Monday mean that skier triggering of small loaded pockets, or steep areas with weak facets near the ground, can still be skier triggered. Some solar triggered sluffing may also occur if the sun comes out.

Weather Forecast

The winds will remain out of the West but start to ease off on Monday with a clearing trend in the morning. Temperatures remain quite mild with valley bottom temperatures above freezing during the day. Flurries are expected later in the day with accumulations of only a couple cm's.

Snowpack Summary

5-10 cm of new snow with warm temps and strong SW winds is loading lee areas and building cornices. 10-25 cm of settled snow sits over the Nov 8 crust. Faceting observed near the ground and around the Oct crust, resulting in easy test results in some areas. Treeline snow depths range from 50-80 cm, with up to 110 cm in wind loaded alpine areas.

Avalanche Summary

On Sunday local ski hills reported ski cutting in alpine lee areas to size 1, and an explosive controlled size 2 on facets near the ground at Lake Louise. No natural avalanche observations but visibility was limited. The skier accidental size 2 on basal facets in Pipestone Bowl on Friday is worth remembering as the snow load slowly increases.

Confidence

Freezing levels are uncertain on Monday

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.