Regions
Banff Yoho Kootenay.
Natural activity is tapering, but conditions are still prime for human triggering. Conservative terrain selection is a must as we transition out of a large avalanche cycle.
Weather Forecast
Continued warm temperatures with freezing levels around 2000m until Saturday AM. The winds have picked up from the west and are forecasted to be in the moderate to strong range at ridgetop until Saturday PM. A small bout of precipitation (5mm) on Friday overnight, but otherwise partly cloudy skies with a clearing trend Saturday AM.
Snowpack Summary
45-70 cm of storm snow overlies either a rain crust or facets from January 30th. This snow combined with warm temperatures has created storm and wind slabs overlying the Jan. 30th interface. The basal facet/depth hoar layers are still active in shallow snowpack areas. Little recovery overnight created isothermal conditions below 1800m today.
Avalanche Summary
Natural avalanche activity is tapering as the snowpack slowly adjusts to the new load. However, moderate to hard sudden collapse snowpack tests today in the Bow Summit area indicate skier triggering is still very possible.
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.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.