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Avalanche Forecast

Archived

Feb 15th, 2020–Feb 16th, 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.

Continued inputs of snow and wind over the last few days have built wind slabs and further developed cornices. With these elements around the potential for avalanches on the deep persistent layer is elevated.

Weather Forecast

The west winds will diminish Sunday to moderate values in the alpine and should stay in that range over the next few days. Light flurries will also continue with alpine temps trending a bit down to -20 values until some expected warming and clearing on Tuesday.

Snowpack Summary

Up to 35cm over the last few days sits over top of a well settled upper and mid-pack. The lower snowpack (bottom 50cm) consists of weaker facets and depth hoar which are well preserved in areas under 150cm HS. These are still producing moderate shears with snowpack tests. Isolated wind slabs exist near ridge tops and lee terrain in the alpine.

Avalanche Summary

The ski-hills worked with a fresh round of wind slabs again today (the same for almost a week straight): small soft slabs up to 40 deep with a few natural cornice falls triggering small slabs. Sunshine Village staff triggered a sz 3, to ground, on the south side of Lookout Mountain: "The Megaldon", with explosives.

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.