Regions
Banff Yoho Kootenay.
Not quite spring "Low", main concerns are deeper facets in thin areas, buried sun crust on solar aspects, and wind slab in lees. Generally great skiing can be found on North aspects.
Weather Forecast
The unsettled weather continues again on Thursday generally cloudy with flurries moving into the region Thursday night. Flurries will continue through to Saturday with accumulations ranging from 10-15 cm.. Friday might be the snowiest day this week and temperatures are forecast to fall below -15 for the start of the weekend.
Snowpack Summary
Convective flurries have deposited new snow in some areas of the park and not so much in others, so the surface conditions are quite variable. Localized windslabs were created earlier in the week and have been reactive. On south and west aspects these slabs may bond poorly to a suncrust down approximately 30-50 cm.
Avalanche Summary
A size 1 windslab was triggered by skiers on a classic leeward slope under a cornice Tuesday - 25 cm deep by 50 m wide. Several large avalanches were triggered earlier in the week. The common theme has been West aspect on suncrust (Amiskwi area - W. of Yoho). In thin areas, the Observation Peak avalanche, released on a deeper layers.
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.