Regions
Kootenay Boundary.
Potential for human triggering of large avalanches remains high. Now is the time to remain disciplined and stick to a conservative approach towards terrain.
Confidence
Moderate - Timing of incoming weather systems is uncertain on Sunday
Weather Forecast
FRIDAY: Mostly cloudy with isolated flurries / Light southwesterly ridgetop winds / Alpine high of -8.SATURDAY: Cloudy with flurries; 5-10 cm of new snow / Moderate southwesterly ridgetop winds / Alpine high of -5.SUNDAY: 10-25cm of new snow / Moderate to strong southwesterly ridgetop winds / Freezing level rapidly rising to around 1500m.
Avalanche Summary
Over a dozen natural and human triggered size 2 storm slab avalanches were reported on all aspects and elevations throughout this region on Wednesday. The new snow was described as "becoming electric with wide propagations and running far and fast". These storm slabs and the persistent slabs beneath them are expected to remain reactive to human triggers.
Snowpack Summary
The snowpack in this region is currently being described as "Complex" and "Spooky".20-30cm of new snow brings recent storm snow total to approximately 55-70 cm which has been redistributed by strong southerly winds. Currently, the primary layer of concern was buried in mid-January and is down around 60-90cm. It is composed of a mixture of surface hoar (weak, feathery crystals) and/or a crust. This layer has been reactive to snowpack tests on all aspects and elevations.Below this layer lies a second crust/surface hoar interface buried early-January that is now 100-120 cm below the surface. The mid-December surface hoar layer is buried 120-150 cm below the surface. This 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.