Regions
Kootenay Boundary.
Wind and storm slabs are still touchy. Use caution venturing into new terrain, especially around treeline.A Special Public Avalanche Warning is in effect for this region.
Confidence
Moderate - Due to the number and quality of field observations
Weather Forecast
The southern interior will be under the influence of a weak high pressure system for the forecast period. Partly cloudy skies with some sunny periods and freezing levels at valley bottom overnight, then rising to around 1000 metres during the day.The next Pacific frontal system will move into the area late Tuesday with freezing level forecast to rise above 2000 metres.
Avalanche Summary
Numerous reports from across the forecast region yesterday of skier accidental, skier remote, skier controlled, explosives testing and natural avalanches up to size 2.5. In some cases, avalanches were triggered within the storm snow and then stepped down to the early January surface hoar layer. Storm and wind slabs will take time to settle and bond. Recent loading has added mass and sensitivity to the deeper early January persistent weak layer. Until the snowpack has time to adjust to the new load, avalanches on this interface will be large and destructive.
Snowpack Summary
Recent snowfall combined with strong ridge top winds formed storm slabs at all elevations these past few days. In some areas dense snow now overlies colder, less-dense snow deposited earlier in the storm. Rece4nt reports indicate this is settling out, improving the skiing dramatically. On solar aspects, the storm snow is resting on a crust with facets around 80 cm below the surface. These facets may be the remnants of a surface hoar layer formed at the beginning of January. Recent testing has shown this facet layer to be reactive, especially in places with no previous skier or rider activity. It appears to be most prominent at treeline and below, and on all aspects. A melt freeze crust from December buried anywhere from 80 to 130cm across the region is still prominent in the snowpack, but no recent avalanche activity has been reported at this interface, however, it is worth keeping an eye on. With additional loading it may become more problematic. Below this, the snowpack is generally well settled and strong.
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.