Regions
Kootenay Boundary.
A cooling trend with light snow falls will slowly drop the avalanche danger. The recent storm slab may need another day or two to settle and stabilise.
Weather Forecast
Moderate westerly winds overnight with light snow and freezing levels dropping down to valley bottoms. Expect 5-8 cm by Saturday morning. Moderate westerly winds continuing on Saturday with some periods of broken skies and freezing levels staying below 800 metres. Light southwest winds on Sunday and Monday with some periods of flurries and temperatures around -10 in the alpine.
Avalanche Summary
Natural storm slab avalanches were reported on Thursday from the Kootenay Pass area during the warm faze of the storm. I suspect that natural activity has stopped, but the persistent weak layer may still be triggered by large loads like a group of sledders or skiers re-grouping.
Snowpack Summary
Warm temperatures settled the recent storm snow, and then a cooling trend tightened the existing storm slab which sits over buried surface hoar in many parts of the region. This surface hoar layer appears to be down 30-40cm and a second more recently buried layer of surface hoar may also be found down around 10-20cm. A thin melt-freeze crust may also be found buried in the upper snowpack but does not seem to be creating an instability. Recently strong south to southwest winds have likely formed new wind slabs in leeward features in the alpine. At lower elevations, warm temperatures and rain have likely melted the surface and a melt-freeze crust is expected to form with the cooling trend. The recently destructive early January surface layer is down 60-100cm and is most prominent on all aspects at treeline and below. It is getting harder to trigger this layer but it is still reactive in snowpack tests suggesting that if you are able to trigger it, the layer is capable of wide propagations and large destructive avalanches.
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.