Regions
Banff Yoho Kootenay.
Good skiing on North aspects. 10-20 cm blanket the Wapta with little wind effect on regular travel routes. Winds pick up Thursday and freezing levels rise causing the hazard to rise as we approach the weekend.
Weather Forecast
Expect clear skies and a good freeze tonight. Very light flurries move in to the region Wednesday and winds will remain generally light from the West with some gusts. Snow picks up for Thursday, along with the wind, and rising freezing levels to 2600 m by Friday. By Sunday, accumulations may be up 10 cm.
Snowpack Summary
Convective cells have dropped 10-20 cm's with light winds over the last few days. Wind slabs 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. Below tree line, snow is isothermal in the afternoons.
Avalanche Summary
Local ski hills reported a few small explosive controlled windslabs in steep unsupported terrain over the past 2 days. Temperatures remained cool today - no pinwheeling observed and crusts remained intact down to 1900 m.
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.