Regions
Banff Yoho Kootenay.
Winds picked up through the day on the Wapta and in the Lake Louise area. Watch for continued windslab development and rising freezing levels over the next few days.
Weather Forecast
Expect a good freeze tonight followed by light flurries for Thursday-Sunday with moderate to strong SW wind. Accumulations will range from 5-20 cm with the greatest amounts occurring West of the Divide and in the Northern part of the region. Freezing levels rise to 2300-2600 m for Thursday and Friday nights.
Snowpack Summary
Convective cells have dropped 10-20 cm's earlier in the week. Windslabs exist in isolated immediate lee features and open areas in the alpine and sit on a variety of hard surfaces. The base of the snowpack is made up of facets and depth hoar and remains weak.
Avalanche Summary
A few small windslab avalanches triggered by explosives or skiers occurred earlier in the week. No new avalanches reported or observed today. Temperatures remained cool again today - no pinwheeling observed and crusts remained intact.
Problems
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.