Regions
Kootenay Boundary.
Conservative route finding is essential to safe travel. Daytime warming and solar input may make buried weaknesses more reactive
Confidence
Moderate - Due to the number and quality of field observations
Weather Forecast
A bit of cloudy weather today and tomorrow, with no precipitation forecast. A ridge of high pressure will rebuild over the province bringing mostly sunny skies with daytime warming and night time cooling for the remainder of the week. Freezing levels may rise to 1200 metres during the day, but should drop to valley bottoms overnight.
Avalanche Summary
Numerous skier controlled, skier accidental, explosive controlled and naturally triggered storm slab avalanches have been reported in the past few days in sizes up to size 3. Yesterday there were 3 skier accidentals in the Bonnington range . A snowmobile triggered 1.5 - 2 was reported in the area east of Kokanee park, on a wind loaded knoll. Most likely these failed as a result of heavy storm and wind loading throughout the past week.. A number of these avalanches released on the February crust interface mentioned in the Snowpack Discussion section. The combination of wind, rapid loading, warm temperatures and increased radiation on solar aspects makes for a perfect recipe for large avalanches.
Snowpack Summary
A considerable amount of snow fell during the past week, with the eastern part of the region receiving the most out of the storms. Reports from across the region indicate that moderate to strong south west winds have redistributed the surface snow into touchy wind slabs. The last storm arrived with considerably less wind and may now be hiding previously formed pockets of wind slab. A melt-freeze crust that formed during the 2nd week of February has been reported at various levels from 50 to 120cm. This crust is widespread and may co-exist with surface hoar or weak facets, especially at treeline and below. This reactive interface is a critical layer to watch in the region, and has been the active layer for some very large avalanches recently. Buried surface hoar layers exist in the drier areas on the west side of the region near Rossland and are worth keeping in mind. Surface hoar growing up to 6mm has been reported in the past 2 days throughout the region. Sun crust may exist on solar aspects at the surface and has also been reported in the region 20cm below the surface.
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.
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.
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.