Regions
Kootenay Boundary.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Sunday: Expect more unsettled skies and lingering flurries, with westerly winds and freezing levels reaching 1500m. 15cm is possible. Monday: Expect the day to begin fairly clear, with a chance of sun poking out in the morning. Clouds should build in the afternoon, with a chance of flurries late in the day. Light southwesterly winds and freezing levels climbing to 1500m. Tuesday: Expect clouds and precip to build, with locally heavy accumulations. Winds continue light to moderate southwesterly with freezing levels around 1500m.
Avalanche Summary
The region has been very active with avalanches the past couple of days. Natural, explosive and human triggered avalanches have been reported up to size 2.5 failing in the storm snow or on the March 26 interface. 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. There was one sympathetic triggered avalanche that released on the early February weakness 150cm deep. Also, several large avalanches (up to size 4.0) were explosive controlled recently. These failed from northeast to northwest aspects at ridgecrest and ran full path to valley bottom, ending as deep moist deposits.
Snowpack Summary
Up to 70cm of new snow has fallen since March 26. Shears within the upper storm snow are tightening with the persistent warm temperatures, although a reactive graupel layer down 25-40 is 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.
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.