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Avalanche Forecast

Archived

Nov 16th, 2019–Nov 17th, 2019

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

Regions

Banff Yoho Kootenay.

A storm is brewing and though total snow/rain amounts are uncertain, avalanche activity will increase.

In areas that receive more than 25cm of new snow, treat the Danger Rating as High!

Weather Forecast

Sunday will see 10-30cm of snow depending on which forecast you're looking at... One thing they all agree on is that its going to warm and windy as the freezing level rises to 2100m with an alpine high of -1 (that means rain at lower elevations). The winds will range from 30-80km/hr from the SW. Snow, wind and temps tapering off on Monday.

Snowpack Summary

10-20cm of settled snow sits on the Nov 8 crust and a variety of old wind slabs in the alpine. Faceting observed around the Oct crust and at the ground showing sudden collapses & propagation propensity in deeper snowpack areas (70-90cm). Treeline snow depths range from 50-80 cm, and up to 110 cm wind loaded pockets in the alpine.

Avalanche Summary

Expect avalanche activity to increase throughout the day on Sunday as the storm progresses.

A skier accidental size 2 slide failed on facets on the ground on a convex feature in Pipestone Bowl, near the Lake Louise Ski area on Friday. Size 1.5 natural on basal facets NE aspect at 2400 m, base of Whitehorn gullies. No other recent observations.

Confidence

Intensity of incoming weather systems is uncertain on Sunday

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.