Regions
Kootenay Boundary.
There is low confidence in the strength of the warm snowpack at all elevations.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Warm temperatures with light precipitation possible for the forecast period. Freezing levels could rise above 3000 m on Friday, before dropping back down on Saturday. Alpine winds are expected to me moderate southwesterlies on Thursday and Friday, before picking up and switching to northwesterlies throughout the day on Saturday.
Avalanche Summary
Reports from Tuesday include evidence of old natural slab avalanches up to Size 2.5. Heavy triggers such as explosives and snowcats were able to trigger 20-90 cm deep storm slabs up to Size 2, but no new naturals were observed and ski-cutting was ineffective.
Snowpack Summary
The rain line during recent heavy precipitation generally hovered around 1700m, although there were periods where rain fell into the alpine. Above that elevation, heavy accumulations of moist, dense snow have been pushed by strong southwest winds into cornices and deeper deposits on the lee side of ridgecrests and terrain breaks. Recent storm snow is poorly bonded to a hard crust, which may have overlying surface hoar, that was buried late January. The mid-December crust/facet/surface hoar weakness may be persisting in the mid to lower snowpack at higher elevations.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.