Regions
Banff Yoho Kootenay.
Avalanche Control on Saturday for the Sunshine Road, please no climbing in the area. Considering control work for Bosworth and Stephen in Yoho and possibly Whymper in Kootenay on Sunday, stay tunned. (LP)
Weather Forecast
The mod to strong SW winds should abate by midnight and flip to a lighter NW flow & cooler temps (-10). Trace precip tonight. Unsettled tomorrow, with sunny periods. High pressure settles in Sunday with clearer skies forecasted.
Snowpack Summary
Since Nov 18th there has been 40-50 cm of new snow along the divide, lots still available for transport. Easy shears at the storm snow interface. There are mod shears on Nov 6 rain crust in the lower third of the pack. The crust exists throughout the region and can be found up to 2400 m.
Avalanche Summary
One notable skier cut size 2.5 avalanche in the Wizard chutes, NW aspect, at 2100 m, on 35-40 degree terrain - 60 cm thick soft slab, propagated 75-80 m, likely slid on the crust & ran 300 m. Generally poor visibility today for avy observations.
Confidence
Due to the number 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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.