Regions
Kootenay Boundary.
If more snow falls than forecasted (>15cm), the danger may be HIGH. Be locally aware of conditions.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Saturday: A system south of the border will send moderate precipitation into the region, accompanied by moderate southwesterlies. 15cm is possible. Freezing levels could climb to 1500m. Sunday / Monday: A series of lows will push precipitation into the region with continued southerly flow and freezing levels reaching 1200m.
Avalanche Summary
Natural, explosive and human triggered avalanches have been reported up to size 2.0 failing on the March 26 interface. 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.There was one sympathetic triggered avalanche that release on the early February weakness 150cm deep.
Snowpack Summary
30-50cm of new snow now overlies the March 26 interface. This has been accompanied by consistently moderate and at times gusty southwesterly winds forming windslabs in lee locations. Cornices loom, and will continue to grow with this weather pattern. The March 26 interface is a crust on all aspects except true north treeline and alpine, where small surface hoar (5mm) is present in sheltered places. The bond between the new snow and this interface is weak, especially where the surface hoar is present. At lower elevations (1600m and below), the high freezing levels have made 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 and rapid loading.
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.
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.
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.