Regions
Banff Yoho Kootenay.
Several skier triggered avalanches over the past 3 days size 2-2.5 in KNP and Sunshine area, see the forecast details. Stick to conservative lines without over head hazard. LP
Weather Forecast
West winds to increase to strong over night & through the weekend bringing snowfall accumulations of up to 30 cm. Most of the snow will occur on Sunday along the Wapta & the Divide. Alpine temperatures will be warm (-2 to -5 range). The hazard will rise through the weekend. Skies will clear Monday as a high pressure moves into the region.
Snowpack Summary
Sunshine, Kootenay and Yoho areas have received up to 75 cm of storm snow since March 2. Lesser amounts of 30-40 cm around Lake Louise and Bow Summit. 40-100cm over the reactive Feb 10 interface of facets,surface hoar,suncrust . Fresh wind slabs up to 40-60 cm deep in the alpine are reactive to skier control.
Avalanche Summary
Over the past three days there have been several skier triggered size 2-2.5 avalanches on the Feb 10th interface in steep terrain or steep convexities in Kootenay and in the Sunshine area below treeline. Avalanche control on the sunshine road produced results up to size 3. Less avalanche activity has been observed in the Louise group.
Confidence
Timing, track, or intensity of incoming weather system is uncertain
Problems
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.
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.