Regions
Banff Yoho Kootenay.
Natural activity has tapered, but human triggered avalanches remain likely.
Weather Forecast
3-5cm Sunday with Moderate SW winds and slowly decreasing temperatures in the afternoon. A fairly benign weather pattern is expected for the start of next week.
Snowpack Summary
Up to 70 cm of storm snow with variable wind effect has put a dense load over the persistent weak layers. In thicker snow pack areas, the Dec. 10th weak layer of facets is now down 80-120cm with a stronger snowpack below. In thin snowpack areas, the Dec.10th layer is mixed in with the basal facets and October crust.
Avalanche Summary
Avalanche control up to size 3.5 today and a natural cycle from 2 days ago. Some ran full path, and many have scrubbed to ground. Many steeper features at treeline & below have also avalanched. The natural activity has tapered, but slopes will remain hair trigger with any further wind loading or by recreationalists on or near a slope.
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.