Regions
Kootenay Boundary.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period
Weather Forecast
Synopsis: A series of weather systems and weak ridges are forecast to cross the province over the next few days. We should see light to moderate snowfall each day. Friday: Flurries ending in the morning, then a mix of sun and cloud. Freezing level around 800 m. Winds are light to moderate from the W-NW. Saturday: 10-15 cm of snow. Freezing level steady around 800 m. Winds increase to strong from the W-SW. Sunday: Moderate snow (15-20 cm). Winds remain moderate to strong. Freezing level rising to 1000 m.
Avalanche Summary
One size 1 natural slab avalanche was observed in a lee feature immediately below the ridge top in the Kootenay Pass area on Wednesday. Expect fresh wind slabs and loose surface snow to be sensitive to human triggers.
Snowpack Summary
Recent winds have been redistributing the low density surface snow onto leeward slopes creating thin wind slabs that have been giving moderate compression tests results. Surface hoar buried at the end of November recently gave moderate to hard but sudden results in compression tests where it has been found as large as 10mm down 90-120cm, or shallower in the Rossland Range where it more of a concern. On a southwest aspect at 2020m in a shallow faceted snowpack area of Kootenay Pass, facets sitting on a rain crust recently gave moderate but resistant compression test results down 30-35cm. Recent reports suggest that the early November facet/crust deep persistent basal weakness has been producing inconsistent, but occasionally sudden snowpack test results and remains a concern. Keep this on your radar, especially when traveling in areas at higher elevations that have a smooth ground cover where the existing crust is uniform and consistent.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.