Regions
Banff Yoho Kootenay.
New windslabs are being formed in lee areas. Slabs can step down to deeper instabilities creating large avalanches that can run full path. Be patient, it will get better.
Weather Forecast
Warmer temps and steady moderate winds are forecast. Along with light snow over the weekend avalanche conditions should remain static.
Snowpack Summary
Up to 70 cm of recent snow with variable wind effect has put a dense slab over the persistent weak layers. In thicker snow pack areas, the Dec. 10th weak layer of facets is now down 100-150cm with a stronger snowpack below. In thin snowpack areas, the Dec.10th layer is mixed in with the October 26 basal facets and crust.
Avalanche Summary
Numerous avalanches were reported today on east and north facing slopes in the Banff area to size 2.5 Thursday. It is likely this was the result of warming temperatures and new wind loading.
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.