Regions
Banff Yoho Kootenay.
Avoid all avalanche terrain and the runouts of any avalanche path.
Weather Forecast
Freezing level to valley bottom Thursday night and a break from the storm. Winds will be in the moderate range. Another significant storm arrived Saturday morning with 30mm expected, alpine winds to 100kmh and freezing levels to 1900-2000m .
Snowpack Summary
30-60cm Thursday and moderate to strong winds have continued to build significant load over a fundamentally weak snowpack. The mix of previous rain, warm temperatures, and this new snow is overloading buried storm and windslabs, as well as the weak basal facet layers.
Avalanche Summary
A historic avalanche cycle is underway, with avalanches up to size 3.5 being widespread. Some are reaching maximal runouts, including onto trails in simple terrain. Avoid all avalanche terrain .
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.