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Avalanche Forecast

Archived

Jan 19th, 2022–Jan 20th, 2022

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.
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.

Tricky conditions currently and some variability throughout the region. Alarming sudden results on the Dec cr in Kootenay today. Several natural and explosive triggered avalanche over the past few days...with more wind on the way to load slopes...

Weather Forecast

Winds increase Wednesday night with snow beginning on Thursday.  5-10 cms of snow is expected with strong W alpine winds and warming temperatures through the day. Friday looks to be overcast with moderate NW winds and light snow.

Snowpack Summary

10-15 cms of low density snow with little wind effect sits on top of windslabs in the alpine and in some treeline areas. These overlie facets in many places resulting in wide propagations in recent avalanches. The Dec. 2 crust and facets are generally 60-90cm deep in the snowpack. Some thin snowpack areas have lingering basal depth hoar and facets.

Avalanche Summary

In the past 48 hrs a small avalanche cycle to size 2 occurred. Avalanche control in Yoho Tuesday produced slabs with every shot. Most were failing on a windslab or facet layer 40-60cm deep and then entraining facets in the track. One stepped down to the November facets ~ 180 cm deep.

Confidence

Due to the quality 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.