Regions
Kootenay Boundary.
Avalanche hazard is forecast to increase throughout the day on Wednesday. Avoid all avalanche terrain during periods of rapid loading from snow or wind.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Tuesday Night: 10-15cm of new snow / Moderate to strong southwesterly ridgetop winds / Freezing level around 700m.Wednesday: 15-20 cm of new snow / Moderate to strong southerly ridgetop winds / Freezing level rising to around 1400m.Thursday: Mostly cloudy with isolated flurries / Light to moderate southerly ridgetop winds / Freezing level dropping to around 900m.Friday: Mostly cloudy with isolated flurries / Light to moderate southwesterly ridgetop winds / Freezing level dropping to around 500m.
Avalanche Summary
On Monday, numerous explosive triggered, size 2 storm slab avalanches were reported near Whitewater and Kootenay Pass. Looking forward, forecast snow and wind will promote ongoing storm slab avalanche activity, especially in higher elevation, lee terrain.
Snowpack Summary
Since last Friday, 15-30cm of new snow fell with the greatest accumulations occurring in the Kootenay Pass area. Moderate to locally strong southwest winds have redistributed the new snow into reactive storm slabs in exposed lee terrain.Approximately 30 - 50 cm of storm snow now covers the most recent crust/surface hoar layer that was buried mid-January. This crust can be found on solar aspects while surface hoar has been buried on shaded aspects above 1600m. Below this layer lies a second crust/surface hoar interface buried early-January that is now 50-90 cm below the surface. The mid-December surface hoar layer is buried 100-140 cm below the surface. This spooky layer still produces "sudden" test results and is most pronounced at treeline, but is also present below treeline . Two laminated crusts created by rain events in late November lay just below the mid-December interface, and may co-exist with facets.
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.
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.