Regions
Banff Yoho Kootenay.
Snowfall amounts are uncertain this weekend but if a significant amount arrives expect avalanche activity on the deep persistent layer.
Weather Forecast
A low over the coast is spreading a stream of moisture to the Southern Rockies while competing polar air overlies our forecast area. The amount of snow that arrives depends on which of these two air masses is the strongest and where the boundary between them ends up varying between 10 and 30cm. Temps and winds will be equally difficult to predict.
Snowpack Summary
Previous strong to extreme W winds have created harder wind pressed surfaces at treeline and above. Surface hoar may be found buried in sheltered locations. Generally the midpack is weak at TL and above, and the entire snowpack is weak BTL. Near the divide, deeper snow-packs are a bit stronger and more supportive.
Avalanche Summary
We had a small avalanche cycle this past weekend due to big winds, but as temperatures have cooled and winds abated, the activity has slowed down significantly. No new avalanches reported or observed Thursday or Friday.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Saturday
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.