Regions
Banff Yoho Kootenay.
Forecasters still have some uncertainty as to how prevalent wind slabs are as a problem due to limited observations.
Weather Forecast
Lows in the -20's Thursday AM and highs around -15C. Some clouds will roll in for the afternoon and a trace amount of snow along the divide. 3000m winds will increase to Moderate from the N/NW but will remain light at valley bottom.
Snowpack Summary
Wide spread wind effect above treeline has created wind slab on NE to SE aspects. Below treeline,30 to 50cm of snow sits over the Jan.17 surface hoar which causes the odd settlement but little activity so far. In shallow areas weak facets and depth hoar exist below the Dec 10 interface. In deeper snow packs this basal weakness is less pronounced.
Avalanche Summary
Some small, loose dry activity out of cliffed areas. Sunshine village reported numerous size 2's with explosives and smaller wind slabs with ski cutting.
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.