Regions
Banff Yoho Kootenay.
Great ski quality to be had, but check for instabilities in the upper snowpack before venturing into bigger terrain. Avalanche control on Mt. Stephen and Mt. Field tomorrow (Sunday), no activities on these peaks during that time.
Weather Forecast
5 cm of snow is expected Sunday with S winds moving into the moderate range aloft. Winds will shift to the NE on Monday. Temperatures will stay cool on Sunday with little solar input.
Snowpack Summary
20-30cm of snow (50cm reported on Wapta!) on Friday with W winds have formed isolated wind slabs in lee features. The March 15 sun crust is down 30-50cm on solar aspects and has produced isolated activity over the past few days.The mid- pack and basal layers have been dormant, but shallow facetted snowpack areas are still worth treating cautiously.
Avalanche Summary
Avalanche control on Mts. Bourgeau and Whymper Saturday saw mixed results, with some size 2 wind slabs being triggered, but many bomb holes as well. Lake Louise ski hill was reporting 2 size 2 avalanches initiated with explosives that were on the March 15 sun crust. Recent cornice falls have produced the same sorts of results.
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.