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Avalanche Forecast

Archived

Dec 18th, 2022–Dec 19th, 2022

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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

Buckle up, extreme cold is in the forecast. Natural activity has slowed, but be wary of steeper slopes where a slab overlies the facets. Where this condition exists, terrain choice will be the only way to reduce the uncertainty about whether a slope will slide.

Confidence

Moderate

Avalanche Summary

No new avalanche observations today.

Snowpack Summary

5-20cm of new snow over the past 2 days sits over a layer of recent surface hoar. At higher elevations, there is variable wind effect. The upper 20-60 cm of snow has formed a slab over the very weak base of facets and depth hoar. Snowpack depths at treeline range between 60 and 120 cm. Below treeline, the entire snowpack is weak and faceted.

Weather Summary

High pressure and -25C to -30C overnight into Monday AM with light E/NE winds and some flurries. Temperatures will continue to drop during the day with clearing skies. Monday night temperatures may get down to -35C or the coveted -40C.

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.