Snowfall amounts are uncertain. If there's heavy snowfall in your area, the local avalanche danger may be higher than forecasted.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Wednesday
Weather Forecast
Synopsis: A strong low pressure system today with wind and mild temperatures is followed by a cool and unsettled air mass through Friday. Conditions will become gradually less windy and less convective but stay generally cooler than normal for the period. Saturday and Sunday the cool north/northwesterly flow will dry out as a ridge of high pressure is very slowly approaching the regions.Wednesday Night: Freezing Level: Valley Bottom. Precip: 10/15mm – 10/25cm Wind: Strong NWThursday: Freezing Level: Valley Bottom. Precip: 2/4mm – 4/10cm Wind: Moderate W gusting Strong/Extreme NW Friday: Freezing Level: Valley Bottom. Precip: 2/4mm – 4/10cm Wind: Light gusting strong NorthSaturday: Freezing Level: 800m No significant precip expected. Wind: Light, SW
Avalanche Summary
On Tuesday a few natural soft slabs were observed that were thought to have occurred in the last 48 hours. Cornice fall to size 1.5 was observed in the Fernie area but the falling chunks of cornice did not initiate avalanches.
Snowpack Summary
As of Wednesday afternoon the storm had yet to impact the South Rockies, but, I suspect it will still deliver a good shot of snow and wind this evening. New storm slabs are likely to develop Wednesday night into Thursday. Wind-loaded slopes and spill zones (fans where snow accumulates below steep faces) may be particularly touchy. A buried rain crust may provide an easy sliding surface for avalanches. This crust is supportive to at least 2100 m in most areas and is up to 9 cm thick. It's thought to be strong enough that snowpack weaknesses below it wont be affected by the load of a person, with the caveat that there may be isolated exceptions (e.g. thin spots near rocks at high elevations). The mid-pack is generally well-settled. Cornices are large and fragile in some areas.
Problems
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.