Regions
Banff Yoho Kootenay.
Watch for windslabs developing with the storm tomorrow. Avalanches could step down into basal weaknesses creating larger than expected events. Whumphing is common and indicates the potential for propagation. Avoid avalanche terrain for a while again.
Weather Forecast
There is great variability in the weather models. Environment Canada is calling for 20cm of snow and high winds on Saturday. Touchy avalanche conditions can be expected as the day progresses, especially in lee areas. If less than 10cm of snow falls, the size of potential avalanches will be greatly reduced..
Snowpack Summary
The majority of the BYK region is a 40-50cm slab of stiff snow overlying 40-50cm of weak facets and depth hoar. This nasty combination has been stabilizing over the past few days but continues to produce whumphing and easy test results. Deeper snowpack areas are stronger, but have a 60-80cm slab over top of the Dec10 surface hoar/facet layer.
Avalanche Summary
No new avalanches observed or reported in the Banff, Yoho and Kootenay region on Friday.
Confidence
Intensity of incoming weather systems is uncertain
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.