Regions
Banff Yoho Kootenay.
A significant storm Saturday has left fresh new windslabs and produced an avalanche cycle. Natural avalanche activity seems to have tapered off with light winds and cold temps but human triggering will remain a concern.
Weather Forecast
As ridge forms, light North winds are bringing cold, dry air to the region through the first few days of the week.
Snowpack Summary
15- 30 cm of snow quickly formed windslabs as it arrived with Strong SW winds Saturday. Below this, through most of the region, a 40-60cm stiff slab sits on a weak base of facets and depth hoar. Deeper snowpack areas display stronger base layers , but have a 60-80cm slab over top of the Dec10 surface hoar/facet layer that remains of concern.
Avalanche Summary
A road patrol in Kootenay today found limited evidence of a mid-storm cycle to sz 2.5 in steep treeline terrain. Saturday, avalanches from Mt Fairview hit Lake Louise and Surprise Pass ran. Lake Louise Ski area reported a sz 3 slab on Unity Peak 450m wide, and size 2 slabs in both Semicircular Bowl and Redoubt Bowl running mid-storm Saturday.
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.