Regions
Banff Yoho Kootenay.
Boxing Day specials on great skiing and Low hazard!Continue to evaluate steep alpine terrain for small wind slabs that are beginning to form.
Weather Forecast
A high pressure system continues to hold bringing cool and stable weather with no new snow in the forecast until at least the 27th. Upper elevation Westerly winds will increase through Saturday. Tree line temperatures should stay between -10 and -16'C.
Snowpack Summary
A well settled snowpack with few weaknesses exists throughout the region. Some small isolated wind slabs exist on leeward slopes in the high alpine. Below 2000m the Dec 3 layer of surface hoar remains visible and produces hard, planar test results in some areas. This weakness is strengthening. Thin snow pack areas are beginning to facet out.
Avalanche Summary
One new natural slab avalanche was observed on a steep N facing hanging snowfield on White Pyramid, 15-20m wide and about 1m deep, possibly cornice triggered. Some sluffing has been observed in really steep terrain due to the increasing winds moving the low density surface snow .
Confidence
Due to the number and quality of field observations
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.