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Avalanche Forecast

Archived

Jan 14th, 2021–Jan 15th, 2021

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

Regions

Little Yoho.

The Jan 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. Have a dig and look for this layer.

Strong winds forecasted for Friday will keep the hazard elevated.

Weather Forecast

Friday will be mainly cloudy with isolated flurries, accumulating up to 2cm of snow. Ridge top winds are forecasted to increase early Friday morning (30-80km/hr from the West) and gradual decrease by the evening. A temperature inversion is also forecasted to move in Thursday evening, expect alpine temps around -5 Friday morning.

Snowpack Summary

15-40 cm of recent snow with the incoming strong SW winds will form wind slabs in exposed locations. The top 120cm in the snowpack boasts 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. The Bow Lake area boasted dozens of avalanches up to sz 2.0. Other notables included Cascade Falls sz 3.0, Pilsner Pillar, Twisted and Silk Tassel up to sz 2.5, Whymper S and N several sz 2-3.0.

Explosive control on Wednesday also produced results up to sz 2.5 on Mt. Bosworth.

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.

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.