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Avalanche Forecast

Archived

Nov 26th, 2020–Nov 27th, 2020

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 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.

Regions

Little Yoho.

We don't have too many observations from this area yet this year, but it sounds like low elevation coverage is improving. Reports of good skiing from the Emerald lake area

Weather Forecast

A big wind event Friday dominates the weather. Chinook conditions east of the divide with warm temperatures and strong westerly winds. Temperatures will stay cooler along the divide, but expect wind. Friday night and saturday we may see up to 15 cm of new snow with higher amounts to the north and winds easing slightly. Sunday looks cold and drier

Snowpack Summary

10-20cm of new snow, along with strong W-SW winds has 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 windslabs were particularly reactive in the Sunshine area with ski patrol triggering avalanches to size 2.5 with explosives. None of these stepped down to the Nov. 5th crust, but some impressive propagations in the new snow.

Lake Louise area saw less reactivity, although windslabs were widespread in the alpine.

Confidence

Wind effect is extremely variable

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.