Regions
Kootenay Boundary.
Potential for human triggering of large avalanches remains possible. Now is the time to remain disciplined and stick to a conservative approach towards terrain.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
SATURDAY: 10-15 cm of new snow / Strong southwesterly ridgetop winds / Freezing level rising to around 1200m.SUNDAY: 10-15 cm of new snow / Strong southwesterly ridgetop winds / Freezing level rising to around 1500m.MONDAY: 10-15 cm of new snow / Strong to extreme southwesterly ridgetop winds / Freezing level rising to around 1800m.
Avalanche Summary
On Wednesday, over a dozen natural size 2 storm slab avalanches were reported on all aspects and elevations, though most occurred at treeline and above. Additionally, several natural persistent slabs to size 2.5 were reported on northwest to easterly aspects above 1900m. 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 cm of new snow brings recent storm snow total to approximately 65-110 cm which has been redistributed by moderate 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. Numerous recent natural avalanches to size 2.5 have been reported on this sensitive layer and human triggering large, destructive avalanches on this layer remains likely.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.