Regions
Kootenay Boundary.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Wednesday
Weather Forecast
WEDNESDAY: Light to locally moderate amounts of precipitation. Moderate northerly winds with a freezing level of 1000-1200m. THURSDAY & FRIDAY: Broken skies with light flurries and light winds. Freezing levels remain steady at 1000-1200m.
Avalanche Summary
The region has been very active with avalanches the past 4 days. Natural, explosive and human triggered avalanches have been reported up to size 2.5. Reports come from all aspects, with a bias to north facing slopes. At lower elevations (where the surface is moist) these are running as loose events and at higher elevations the new snow is propagating as a slab. Remote triggering has also been observed.
Snowpack Summary
Up to 100cm of new snow has fallen since March 26. Shears within the upper storm snow are tightening with the persistent warm temperatures, although a reactive layer down 40-50cm remains. The March 26 interface is a melt freeze a crust on all aspects except true north treeline and alpine, where small surface hoar (5mm) is present in sheltered places. The bond at this interface is gaining strength, with lingering concerns on true south aspects where the crust is thickest and where the surface hoar lurks. At lower elevations, the consistent high freezing levels have kept the new snow heavy and moist. The deep, persistent early February surface hoar lingers in the snowpack giving sudden results in testing. Concern remains with heavy triggers (cornice), step down avalanches and rapid loading from intense precipitation, strong winds or sun.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
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.