Regions
Kootenay Boundary.
Warm temperatures and sunny breaks are on the menu for Friday. Use caution in steep open terrain and around large overhanging cornices.
Weather Forecast
Friday: Cloudy with sunny breaks. The freezing level is between 2500-3000 m. Ridge winds are light to moderate from the west. Saturday: Cloudy with possible light snow. The freezing level lowers to around 1800-2000 m. Winds are generally light from the W-NW. Sunday: Cloudy with light snow and occasional sunny breaks. The freezing level is around 1400-1500 m.
Avalanche Summary
Only one size 1 skier controlled avalanche on a steep convex roll was reported on Wednesday. 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
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.