Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Regions
Banff Yoho Kootenay.
Continued snowfall with strong winds overnight will increase the danger at all elevations Monday. Plenty of reports of avalanche activity and a couple close calls over the last two days mean this is a good time to stay out of avalanche terrain.
Weather Forecast
Strong SW winds accompanied by moderate snowfall amounts should continue through Sunday night with snowfall amounts of 10-15 cm. Temperatures will remain in the -5 to -10'C range. The winds and snowfall start easing Monday morning with temperatures cooling, then remaining steady until a slight rise on Wednesday.
Snowpack Summary
Strong SW winds with 5-15cm of new snow in the last 24 hours are creating slabs in lee areas at treeline and above which are reactive to skiers. The snowpack at treeline is from 60-90 cm deep across the region. The main feature in the snowpack is a buried layer of facets now down 30 to 50 cm and sitting on the Halloween crust in areas below 2700m.
Avalanche Summary
Continued reports of natural and skier triggered avalanche activity on Sunday. Local ski hills reported easily triggered wind slabs and persistent slabs up to size 2 with ski cutting and explosives. Several reports of natural avalanches in back country areas around Bow Summit and Emerald Lake, and one avalanche incident on Mt Crowfoot.
Confidence
Intensity of incoming weather systems is uncertain on Monday
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.