A Special Public Avalanche Warning applies to this region. Don't lower your guard yet. Strong winds will do their part to maintain touchy conditions and elevated avalanche danger on Saturday.
Confidence
Moderate - Freezing levels are uncertain on Sunday
Weather Forecast
Friday night: Flurries bringing 5-10 cm of new snow. Winds strong to extreme from the southwest.Saturday: Mainly cloudy with isolated flurries and a trace of new snow. Winds moderate to strong from the west. Freezing level reaching approximately 800 metres with alpine temperatures around -8.Sunday: Mainly cloudy. Winds moderate to strong from the southwest. Freezing level rising to approximately 1500 metres with alpine temperatures of -4.Monday: Cloudy with sunny periods. Winds light from the southwest. Freezing level to 2000 metres or potentially higher with alpine temperatures +1.
Avalanche Summary
Reports from the Fernie area indicate widespread natural, skier controlled, as well as remotely triggered avalanche activity to size 1.5. One Size 3 avalanche ran naturally in steep alpine terrain in the late afternoon on Thursday. Most avalanches have been isolated to the depth of 40cm in the most recent moist storm snow and activity has been noted at all elevations and on all aspects. Previously buried surface hoar, facets, and/or a sun crust may increase the reactivity and propagation propensity of storm slabs.
Snowpack Summary
Up to 35mm of precipitation fell over Thursday night, with periods of rain leading to diminished new snow amounts of around 15-25 cm at treeline elevations. This precipitation fell over the roughly 40cm of moist new snow from Thursday, adding additional load to the 60-80cm of storm snow that accumulated in the region last weekend. Strong shifting winds redistributed the previous storm's snow in exposed terrain forming touchy wind slabs. These wind slabs are now obscured by the latest round of snowfall. The combined accumulation of multiple storms' snow now overlies a highly variable old surface which included wind affected surfaces, a layer of surface hoar in sheltered areas, facets, and/or a thin sun crust. Recent reports suggest a poor bond between the new snow and the old surface. The mid and lower snowpack are generally well settled and stable but isolated basal weaknesses may exist in shallow snowpack 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.