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Avalanche Forecast

Archived

Feb 12th, 2020–Feb 13th, 2020

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

Regions

Banff Yoho Kootenay.

Another 48-hour break between wind storms gives a nice few days. We continue to be concerned about isolated, large avalanches releasing on the deep facet layer. For this reason we recommend avoiding travel directly through avalanche start zones.

Weather Forecast

A ridge of high pressure will keep the weather over our region mostly fine for Thursday with just a trace of snow here and there and temps ranging from -7 to -12. The wind comes up again on Thursday afternoon/evening, forecast to reach 100 km/hr. 5 cm per day expected for Friday and Saturday.

Snowpack Summary

5-10 cm of dry snow over the past 24-hours brings the 7-day storm total to 25-40 cm across the region. Light winds today kept the surface soft, but strong winds on Tues may have left some lingering wind slab in high alpine areas. We remain very concerned about the facetted weakness deep in the snowpack and continue to urge avoidance of start zones.

Avalanche Summary

We were surprised by the lack of wind slab activity reported on Wednesday, considering the extreme winds on Tuesday - however we have no observations from the high alpine. The ski area teams today reported numerous size 1 loose dry sluffs running quite far, as well as one 24-hr old size 2 deep slab on Fatigue Mountain near Sunshine.

Confidence

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.