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Avalanche Forecast

Archived

Nov 18th, 2019–Nov 19th, 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.

Heavy loads (explosives) producing size 2 avalanches on the October crust. Keep on the look out for wind-slabs at your local level.

Weather Forecast

Light precip (7-10cm) followed by a cooling trend is expected Tuesday. Winds will also abate, however wind velocity will rise and fall from the moderate range to calm over the next few days. Clearing expected early Thursday.

Snowpack Summary

Yesterday, 5-10 cm of new snow with warm temps and strong SW winds was loaded in lee areas and built cornices. 10-25 cm of settled snow sits over the Nov 8 crust. Faceting observed near the ground and 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

Lake Louise ski area was reporting that explosive control was producing wind-slabs that would step down to the Oct crust producing numerous size 2 avalanches.

Confidence

Wind effect is extremely variable 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.