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Avalanche Forecast

Archived

Jan 15th, 2021–Jan 16th, 2021

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.

The January 11 surface hoar is buried by up to 40cm of recent snow and has proven to be sensitive to human triggering where it is found. Take the time to dig to look for this before committing.

Continued winds will keep hazard raised into the weekend.

Weather Forecast

Winds shift to the NW gusting 40 to 60km/h in the alpine into Saturday as a ridge forms over the region. Valley bottom temperatures will approach 0C Saturday as alpine temperatures rise from -15C over night. Winds shift back West late Saturday as the next system ,a bit to the North, brings the potential for a temperature inversion and light precip. 

Snowpack Summary

15-40 cm of recent snow has been redistributed in the alpine and open areas into treeline by mod to strong SW winds. The top 120cm in the snowpack displays 4 persistent layers. The Jan 11 surface hoar (6mm) is down 15-40cm and remains reactive where found. The Dec persistent layers are less reactive but produce sudden results when they fail.

Avalanche Summary

A widespread natural avalanche cycle occurred on Wednesday up to sz 3.0. Most were alpine windslabs or treeline storms slabs. Others of note: Cascade Falls sz 3.0, Pilsner Pillar, Twisted and Silk Tassel to sz 2.5, Whymper S and N several sz 2-3.0.

Explosive control at the ski hills Friday created small windslabs 10-20cm deep but limited to sz 1-1.5

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.

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.