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Avalanche Forecast

Archived

Jan 12th, 2021–Jan 13th, 2021

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

Regions

Banff Yoho Kootenay.

An intense storm tonight and into Wednesday morning will cause an increase in avalanche hazard. Avoid avalanche terrain Wednesday.

Weather Forecast

20-40 cm forecasted overnight and Wednesday morning with strong S-SW wind.  Temperatures will remain warm for much of the storm which will promote rapid slab formation and cornice growth.  The cold front moves through the region Wednesday morning with temperatures dropping, winds easing and precipitation stopping by noon on Wednesday.

Snowpack Summary

The recent storm snow coupled with strong S-SW winds may not bond well to underlying surfaces.  Below this, there are three persistent weak layers from Dec are down 30-100 cm that may become touchy with critical loading,  The Nov. 5 basal crust/facets may also become reactive with the in areas that receive rapid loading from the storm.

Avalanche Summary

No new avalanches reported Tuesday. Yesterday, climbers triggered a size 1 slab enroute to their climb in Balfour Creek.  Over the past few days on Mt. Field, there was one cornice triggered size 2 slab avalanche was observed in the alpine and a triggered size 0.5 slab in a very steep open glade just below treeline.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.