Regions
Kootenay Boundary.
The danger ratings assume around 10 cm new snow. If there is more new snow, bump up the danger ratings!
Confidence
Moderate - Forecast snowfall amounts are uncertain on Monday
Weather Forecast
A front passing through on Monday is expected to bring around 10 mm (up to 25 mm at Kootenay Pass is possible) precipitation and moderate to strong SW winds (switching to NW post-front), with the freezing level falling from around 2500 m to 1500 m. Cloud and a few snow showers may linger on Tuesday morning, before a ridge brings dry and very warm weather again.
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. Warming-related avalanche activity should ease with the passage of a cold front on Monday.
Snowpack Summary
Large cornices overhang alpine slopes and threaten to trigger avalanches on slopes below. New snow will be landing on mainly moist or crusty snow surfaces. 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. Test results are variable, with occasional sudden planar (pop) results. While generally unlikely to trigger, this layer could produce surprisingly large avalanches with a cornice fall or warm temperatures.
Problems
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.
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.