Regions
Kootenay Boundary.
Strong SW wind and fresh snow Friday night may fuel another round of natural avalanches while most of us sleep. Light wind and lack of snowfall on Saturday may appear benign, but the mountains are currently primed for human triggered avalanches.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Saturday
Weather Forecast
A deep upper trough is moving through BC this weekend. The unsettled weather pattern should deliver continued precipitation and southwesterly winds to the mountains of the Kootenay Boundary through the forecast period. FRIDAY NIGHT: 5 to 20 cm of snow, strong to extreme southwest wind.SATURDAY: Overcast skies, freezing level beginning around 500m rising to 1000m in the afternoon, moderate SW wind, 5 to 10 cm of snow. SUNDAY: Overcast skies, freezing level beginning around valley bottom rising to 500m in the afternoon, light SW wind, 1 to 5 cm of snow. MONDAY: Overcast skies, freezing level beginning around valley bottom rising to 500m in the afternoon, moderate SW wind, 1 to 5 cm of snow.Visit avalanche.ca/weather for a more detailed mountain weather forecast.
Avalanche Summary
On Thursday control work produced storm slab avalanches to size 1.5 on NE, E and SE facing slopes. Reports from Wednesday include numerous natural, skier and explosive triggered storm/wind slab avalanches up to Size 2.
Snowpack Summary
30 to 80cm of snow has fallen in the last week, which is bonding poorly to a sun crust on previously sun-exposed slopes, or facets and large surface hoar on shaded aspects. Wind slabs have formed in exposed areas from winds out of the NW and now SW, with continued snow and wind forecast for Friday night and Saturday. A variety of crusts and thin surface hoar layers in the upper snowpack are becoming more of a concern with this increased load. Areas with a shallow snowpack (less than around 170 cm) generally have a weak snowpack structure with a deep persistent weakness of facets near the ground. There are a number of great MIN reports from Thursday and Friday here: https://avalanche.ca/mountain-information-network/submissions/
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.