Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
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.
We expect a natural avalanche cycle to start Friday and continue to Saturday night. Avoid avalanche terrain as conditions will change rapidly on Friday. Good ski conditions at lower elevations out of the wind. SH
Weather Forecast
Another 30-50cm is expected by Saturday night at treeline elevations. Alpine winds will be in the strong range and freezing levels to 1900m Friday.
Snowpack Summary
25-50cm of recent storm snow sits on a crust from January 30, which exists up to 2300m on all aspects (higher on solar aspects). In isolated locations this has been blown into soft slabs.Over the next two days this bond to the Jan. 30 interface will be critical. The basal depth hoar, facet layer may also be "woken up" with the additional load.
Avalanche Summary
One natural size 2 avalanche was observed on Mt. Redoubt near Lake Louise yesterday which stepped to the basal weakness, was 60 m wide and failed on the ground level depth hoar. Another group today triggered a size 2.5 which was almost 2m deep on a crossloaded treeline feature above Bow Summit. Yikes! This failed on the Basal facets/Depth hoar.
Confidence
on Friday
Problems
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.
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.