Regions
Kootenay Boundary.
Avalanche hazard is expected to decrease as things dry out and cool off.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
The stormy pattern is expected to continue on Wednesday before a drying trend later in the forecast period. Wednesday: After heavy precip and high freezing levels overnight, expect another 5-10cm during the day with freezing levels down to 1800m and strong southwesterly ridgetop wind. Thursday: 2-5cm of snow, freezing level in valley bottoms and light to moderate southwesterly ridgetop wind. Friday: Mainly cloudy with light flurries possible, freezing level near valley bottom and moderate southerly ridgetop wind.
Avalanche Summary
On Saturday natural storm slab avalanches to size 2 were reported on East, North, and Northwest facing features between 1900 and 2100m. These were likely running on the early December surface hoar. On Sunday control work in the region produced numerous avalanches to size 2 on SW, S and SE facing aspects between 1900 and 2000m. Late Sunday we received a report from the Rossland range where a group of skiers triggered a size 2.5 avalanche on a north facing piece of terrain at 1700m. The avalanche initially failed at the Mid-November crust before stepping down to the ground. Thankfully, it sounds like everyone involved will be okay.
Snowpack Summary
Continued snowfall brings total treeline snowpack depths to 150-200cm. 50-100cm of storm snow since early December is bonding poorly to a variety of old surfaces including facets, surface hoar, and/or a crust at upper elevations (especially on southerly aspects). The most critical of these is the buried surface hoar, which has the potential for remote triggering, extensive releases and prolonged sensitivity to triggers. It is likely lurking in most sheltered areas treeline and below. The thick mid-November crust is just under this weakness.
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.