Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
Banff Yoho Kootenay.
The natural avalanche cycle is expected to taper off but the new slab formed by storm snow over the basal facets will likely continue to create large avalanches for some time. Avoid all avalanche terrain for the next while until things settle down!
Weather Forecast
Moderate to strong W winds with strong gusts are expected to continue for the next 2 days with cloudy skies. The precipitation has ended. Alpine temperatures will be around -7C with overnight lows of -10. Winds will abate by Thursday and skies will become a mix of sun and cloud.
Snowpack Summary
Up to 80 cm of storm snow has fallen over the last few days, combined with very strong winds. Deep storm slabs have formed from new snow and wind loading; in excess of 120 cm in leeward areas. These slabs are overloading a weak, facetted snowpack. The precipitation has ended, but strong gusty West winds are expected to continue for the next 2 days.
Avalanche Summary
Large avalanches to size 3 continue to occur with some running full path. A size 2 in White Rabbit (near Louise ski area) released to ground, causing several sympathetic size 1's. Numerous human triggered avalanches were reported adjacent to ski areas including Ptarmigan Chutes today and Maintenance Cliffs and a close call on Wawa Ridge yesterday.
Confidence
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.