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Avalanche Forecast

Archived

Dec 17th, 2021–Dec 18th, 2021

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

Regions

Banff Yoho Kootenay.

As a Pacific system arrives Saturday we expect modest snowfall amounts and a significant increase in the winds to raise avalanche hazard through the weekend.

Weather Forecast

A Pacific Low approaches the region Friday night. Ahead of the warm front, expect winds to increase reaching strong in the alpine as snow arrives Saturday morning. The current alpine temperature inversion will break down. Snow amounts range from 5 -15 cm favoring the divide and west before a high pressure system clears the region midday Sunday.

Snowpack Summary

15-25 cm of low density surface snow with extensive wind effect in the alpine. There is a Dec 2 rain crust present below 2200 m and down 40-60 cm with facets above and below. The Nov 5 crust/facet interface is found near the base of the snowpack and has been responsible for deep persistent slabs. Snowpack depths at treeline are from 120 to 180 cm.

Avalanche Summary

Ski patrols reported limited results with explosive work and skier control efforts today: mainly small slabs to sz 1.5 in lee features. A size 3.5 natural avalanche failing on glacier ice above the Bow Hut approach occurred in the last few days. This appeared to be triggered by wind loading and shows some of the uncertainty in the snowpack.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

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.