Regions
Banff Yoho Kootenay.
The first major avalanche cycle of the season will peak on Thurs. Avoid all avalanche terrain. There is a significant weak layer deep in the snowpack that is active and we expect widespread avalanche activity.
Weather Forecast
A strong south-westerly flow dominates the region bringing rain, snow and warm temperatures. Rain is expected to reach 2200m Thursday morning followed by snow as the moist air lifts over the colder incoming air. Thursday evening should be winter again with colder temps and snow..
Snowpack Summary
The snowpack near treeline has a variable depth between 60cm and 1m. The main feature of concern is a facet layer associated with the halloween raincrust. This layer has been causing avalanches, extensive whumphing, and has had good propagations.
Avalanche Summary
Visibility was generally poor throughout the forecast area but some slab avalanches to size 2.0 were noted throughout.
Confidence
Timing, track, or intensity of incoming weather system is uncertain
Problems
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.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.