Regions
Kootenay Boundary.
Significant snowfall, strong winds and mild temperatures will add new load to an already complex and reactive snowpack. Avoid all avalanche terrain until the new snow has had a chance to settle and stabilize.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
TONIGHT: Wet snow and rain. Precipitation 10-20 mm. Ridge wind strong, southwest. Temperature 2. Freezing level rising to 2000 m.THURSDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind strong, southwest. Temperature 2. Freezing level lowering to 1500 m.FRIDAY: Mostly cloudy, flurries. Accumulation trace. Ridge wind light, southwest. Temperature -2. Freezing level 1200 m.SATURDAY: Cloudy, flurries. Accumulation trace. Ridge wind light, southwest. Temperature -2. Freezing level 1100 m.
Avalanche Summary
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.Sunday there were reports of natural loose wet avalanches to size 2.5 on solar aspects as well a size 3 deep-persistent, slab avalanche on a northerly aspect that's suspected to have failed on the December 15th 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.About 5 cm of new snow now covers the January 16th surface hoar/ crust layer that formed during the most recent period of warm weather and clear nights. This crust can be found on solar aspects while surface hoar has been buried on shaded aspects above 1600m. Below the January 16th crust lies the January 5th interface which also consists of a crust/surface combination and is buried 45-70 cm below the surface. The late-December surface hoar layer is buried 75-100 cm below the surface, and the spooky mid-December surface hoar layer is now 80-130 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.