Regions
Banff Yoho Kootenay.
Snow is in the forecast for the week, starting on Sunday night. Accumulations up to 20 cm are possible by the middle of the week. Pull in the reins once there is new snow on the ground, as the fresh stuff won't bond well to the current snow surface.
Weather Forecast
The weather pattern is changing for the week ahead, with flurries starting overnight on Sunday but only minor accumulations for Monday. Temperatures should remain in the -5 to -12 range. Expect more snow through the week, although we doubt the models slightly and expect perhaps up to 20 cm by the end of the week.
Snowpack Summary
No new snow in several days. Old wind slabs 10-40cm deep linger in immediate lee areas of the alpine. The October 26th crust/facet layer is ~30 cm above ground. In many areas the entire snowpack is faceting and becoming quite weak. Snow depths range from 50-85 cm at 2000 m.
Avalanche Summary
No new avalanches reported or observed today, but as recently as Saturday someone triggered a nasty looking size 2 on the SE slopes of Cirque Fore-Peak at 2700m above Helen Lake. Two skiers were caught on the flanks of a slab 20-40cm deep, 80m wide, running up to 250m with no burial but they some lost equipment.
Confidence
Forecast snowfall amounts are uncertain on Tuesday
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.