Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 11th, 2022–Dec 12th, 2022

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

Regions

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

Yesterday, we transitioned the persistent slab into a deep-persistent slab problem and this will likely remain for some time. Conservative terrain choices are recommended.

Confidence

Moderate

Avalanche Summary

Lake Louise ski patrol was able to trigger two size 2 avalanches with explosives today, both had fracture lines as deep as 50cm. Notably, a member of the Sunshine patrol triggered a size 2.5 (skier accidental, deep persistent slab) that was 60 meters wide and averaged 75cm deep. The bed surface was on the ground. The patroller was able to ski out to the side safely. Also, they produced many size 1 avalanches with ski cuts and explosives.

Snowpack Summary

Recent snow and moderate SW winds have formed wind slabs at higher elevations. In most other areas, 20-50 cm of snow is forming a soft slab over a very weak base of facets, with occasional thin crusts at the interface. Average snowpack depths at treeline are between 60 and 90 cm.

Weather Summary

Temperatures are expected to be relatively warm over the next few days with the alpine reaching -7 and the valley's close to zero. No significant precipitation will occur. Alpine winds are going to die down to the light range on Monday.

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.