Regions
Banff Yoho Kootenay.
Sporadic natural activity has been seen in the alpine, and human triggered avalanches are still possible at all elevations. We have a structurally weak snowpack and a wide margin of safety is required.
Weather Forecast
Cloudy skies with light North winds and flurries producing small amounts of snow are forecast for Sunday. Cooler temperatures in the -18 to -20C range are expected in the alpine.
Snowpack Summary
There is 15-25 cm of low density storm snow at tree line with a thin rain-crust below the storm snow at lower elevations. Wind effect on open slopes at tree line and above. Common throughout the region are the weak facets and depth hoar in the lower half of the snowpack, particularly at lower elevations and east of the divide.
Avalanche Summary
Wind triggered sluffing but no new slab avalanches observed on Saturday. Sporadic natural and human triggered avalanches on the weak facets of the lower snowpack continue. Two size 2.5 natural avalanches were observed within the last 48 hours on E-SE aspects in the alpine on Mount Ball and Mount Brett. Both appeared to scrub down to the ground.
Confidence
Due to the number of field observations
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.
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.