Regions
Kootenay Boundary.
If the sun peeks out, a round of natural avalanches may occur.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain on Tuesday
Weather Forecast
Cloud, moderate to strong NW winds and a few snow showers may linger on Tuesday morning, before a ridge brings dry and very warm weather again for the remainder of the week. Freezing levels are expected to climb above 3000 m by Wednesday.
Avalanche Summary
A natural cycle of size 1-2 loose wet avalanches continued though the week and into Saturday. On Friday, an explosives control mission near Nelson produced several size 2-3 wet slab avalanches. A size 3 cornice-triggered slab also released naturally.
Snowpack Summary
Large cornices overhang alpine slopes and threaten to trigger avalanches on slopes below. New snow will have landed on moist or crusty snow surfaces, and may have been shifted by strong winds into wind slabs. At low elevations, the snowpack is isothermal. The late February surface hoar/ crust interface (down 80 to 130 cm) remains a low probability/ high consequence concern. While generally unlikely to be triggered, this layer could produce surprisingly large avalanches with a cornice fall or warm temperatures.
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.