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Avalanche Forecast

Archived

Dec 15th, 2022–Dec 16th, 2022

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

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Increasing winds through Friday will move loose surface snow around in alpine terrain. Although we don't expect a large loose dry cycle, this could be enough of a trigger for one of the deeper weak layers.

Confidence

Low

Avalanche Summary

Over the past few days, both ski hills have triggered deep slabs up to size 2 with explosives or sometimes with a ski cut after the explosive failed to trigger the slope. Parks Forecasters have noted large whumphs in the Sunshine Backcountry on Tuesday and in the O'hara region on Wednesday. No new naturals have been observed for the past few days.

Snowpack Summary

20-60 cm of snow has formed a slab over a very weak base consisting of facets. Thin crusts can be found on the facet interface at lower elevations and on solar slopes. Snowpack depths at treeline range between 60 and 120 cm. Below treeline, small sluffs may be triggered in steep features where the ski and foot penetrations are to the ground in a very weak facetted snowpack,

Weather Summary

Friday: Alpine high -10, low -20. Winds moderate to strong NW. In the late afternoon and overnight, there may be localized heavy flurries with the descent of a strong cold front. On the Eastern slopes, we may see up to 10 cm, elsewhere, 2-5 centimetres.

Saturday: Alpine high -20, dropping to -25 throughout the day. Alpine winds will ease to light NE. 5 cm of snow.

Sunday: Alpine temperatures will continue to cool -25 to -35 range with light NE winds. Expect some clouds and light flurries on the East slopes.

Terrain and Travel Advice

  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Uncertainty is best managed through conservative terrain choices at this time.

Problems

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.