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Avalanche Forecast

Archived

Nov 27th, 2020–Nov 28th, 2020

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

Weather Forecast

Up to 10-15 cm expected along the Divide, with the highest amounts expected on the West side in higher terrain.  Strong winds should ease early Saturday and through the day.  Temperatures will also fall slightly on Saturday.  Sunday looks cooler, mix of sun and clouds with winds picking up through the day.

Snowpack Summary

Alpine terrain scrubbed by recent strong W-SW wind created windslabs at treeline and above. The Nov 5 facet/crust combo is down 50-80 cm and producing variable test results from easy to hard, but 'sudden' in fracture character. The Nov crust extends up to 2500 m on N aspects and higher on solar aspects. Snow depths at treeline are 70-130 cm.

Avalanche Summary

New touchy cornice growth in the last 24 hrs. Sunshine forecasters report stubborn windslabs at treeline 10-15 cm think. Lake Louise area saw less reactivity. One recent size 2.5 avalanche observed on a steep moraine lee feature at 2100 m, in the path next to the Takakkaw Falls hostel. The crown was 60-70 cm deep and propageted about 80 m.

Confidence

Due to the number of field observations

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.