Regions
Kootenay Boundary.
Deep instabilities are still present in our snowpack. Conservative terrain selection remains critical.
Confidence
Moderate - Freezing levels are uncertain on Wednesday
Weather Forecast
Tuesday: 4-8cm of new snow / Moderate to strong southwesterly winds / Freezing level at 8000mWednesday: 15-30cm of new snow / Moderate southerly winds / Freezing level at 1200mThursday: Light flurries/ Light southwesterly winds / Freezing level at 800m
Avalanche Summary
On Sunday a few skier and explosives-controlled storm slab avalanches to size 1.5 were observed failing on west to northeast facing slopes between 1900m and 2050m. These avalanches occurred in response to new snow and wind. No persistent avalanches were observed over the weekend. That isn't to say that weaknesses don't exist in the snowpack and that large avalanches aren't possible. It was only a few days ago when explosives control produced a size 2.5 and a size 3 slab avalanche that stepped down to the mid-December layer on north to northwest aspects above 2000 m. Over time, we'll likely transition to a low-probability/ high consequence avalanche pattern with these buried persistent weak layers. This makes terrain selection harder as some slopes may not react to the weight of a rider, while other slopes may be waiting to surprise with nasty consequences.
Snowpack Summary
Since last Friday between 15 and 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.