Regions
Kootenay Boundary.
Recent loading from new snow and wind has added to an already complex and tricky snowpack with several buried weak layers. Best to stick to moderate terrain and avoid wind-loaded areas.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
TONIGHT: Flurries. Accumulation trace. Ridge wind light, southwest. Temperature -6. Freezing level 500 m.SUNDAY: Flurries. Accumulation 5-15 cm. Ridge wind strong, south. Temperature -3. Freezing level 1200 m.MONDAY: Flurries. Accumulation 5-10 cm. Ridge wind moderate, southwest. Temperature -4. Freezing level 1200 m.TUESDAY: Mostly cloudy, flurries. Accumulation trace. Ridge wind light, south. Temperature -5. Freezing level 800 m.
Avalanche Summary
Friday there were reports of a few natural, size 1-1.5 storm slab avalanches in steep terrain. Also, two size 1, skier accidentals were triggered in steep terrain within the recent storm snow.On Thursday ski cuts and explosive control work produced numerous size 1.5-2 storm slab avalanches as well as a size 2.5 and a size 3 that stepped down to the mid-December layer on north to northwest aspects above 2000 m. .Wednesday there were reports of a skier accidentally triggering a size 1 wind slab on an east aspect at 2000 m that is suspected to have failed on the most recent mid-January surface hoar layer. And a very large whumpf was observed on a northeast aspect at 1800 m that is believed to have been associated with the mid-December layer.
Snowpack Summary
The snowpack is complex with several buried weak layers of concern that remain active and have produced several recent, large and destructive avalanches.Approximately 20-40 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 and continues to produce sudden snowpack test results. This spooky layer 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. In shallow, rocky terrain the mid-December surface hoar and the late November crust seem to be reacting together which is a volatile combination.
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.