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Avalanche Forecast

Archived

Dec 14th, 2022–Dec 15th, 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 on Thursday and 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

Lake Louise patrol noticed a size 1 windslab that failed naturally overnight. Sunshine patrol was able to trigger one size 2 deep slab with a cornice shot with explosives. Parks forecasters noted several large whumphs in the Sunshine Backcountry today.

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. Expect to find lingering wind slabs at higher elevations. Snowpack depths at treeline range between 60 and 120 cm.

Weather Summary

Thursday: Alpine highs -8 to -15, lows -20. Winds moderate NW. No precipitation.

Friday: Alpine high -12, low -20. Winds moderate to strong W. No precipitation

Saturday: Alpine high -20, dropping to -24 throughout the day. Alpine winds dropping to light NE. 2-4 cm of snow.

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.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.

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.