Regions
Kootenay Boundary.
Danger ratings trending down due to low freezing levels after the recent rain.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Mostly clear skies with light Southeast winds overnight. Freezing levels dropping down to valley bottoms and overnight alpine temperatures around -8. Clear with light Southeast winds on Monday and alpine temperatures around -5. Cloud developing on Tuesday as the light winds shift to the South or Southwest and alpine temperatures stay around -7. There is a chance of light flurries with little accumulation on Tuesday. On Wednesday expect mostly cloudy with some sunny breaks and light Southeast winds.
Avalanche Summary
No new reports of avalanches from this region
Snowpack Summary
Rain from the past week has saturated the snowpack in most areas, and a hard crust likely exists to about 2100m. The thickness of the crust will depend on elevation and how much rain fell. The Kootenay Pass is reporting a 9 cm knife hard crust with 5 cm of new snow above, and closer to Nelson up to 2000 metres elevation we have reports of a 7 cm knife hard crust with 1 cm of new snow above. At higher elevations, snow and strong winds have added depth and cohesion to a storm slab which may be sitting on a weak layer of hard rain crust, facets, and/or surface hoar. Near the base of the snowpack is a crust/facet combination which formed in November. This interface remains a concern at higher elevations in many parts of the region as it continues to produce whumpfing, and has the potential for wide propagations.
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.