Regions
Kootenay Boundary.
Recent loading from new snow and wind are adding to an already complex snowpack with several buried weak layers. Best to stick to simple terrain with no overhead hazards until the snowpack adjusts.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
TONIGHT: Flurries. Accumulation 2-5 cm. Ridge wind moderate, southwest. Temperature -5. Freezing level 700 m.SATURDAY: Flurries. Accumulation 2-5 cm. Ridge wind moderate, southwest. Temperature -4. Freezing level 1000 m.SUNDAY: Snow. Accumulation 10-20 cm. Ridge wind strong, south. Temperature -4. Freezing level 1200 m.MONDAY: Flurries. Accumulation 2-5 cm. Ridge wind moderate, southwest. Temperature -5. Freezing level 1000 m.
Avalanche Summary
On Thursday 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. Ski cutting also produced numerous size 1-1.5 on all aspects from 1500-2100 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 January 16th surface hoar layer, as well as a very large whumpf on a northeast aspect at 1800 m that is believed to have been associated with the mid-December layer.On Monday there were reports of two skier accidentals triggered on a northwest aspect between 1980-2000 m. The first was a size 1.5 and the second, triggered about thirty minutes later, was a size 2. A natural size 2 loose wet avalanche was also report on a southwest aspect at 2100m, as well as numerous explosive triggered size 2-3.5 slab avalanches running on weak layers deep in the snowpack.
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 20-30 cm of storm snow now covers the January 16th surface hoar/ crust layer. This crust can be found on solar aspects while surface hoar has been buried on shaded aspects above 1600m. Below the January 16th layer lies the January 5th interface which also consists of a crust/surface combination and is buried 50-90 cm below the surface. The spooky mid-December surface hoar layer is now 100-140 cm below the surface. This spooky interface continues to produce sudden snowpack 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. 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.