Regions
Kootenay Boundary.
This is the first big warm-up after some significant snowfall. A warming-related avalanche cycle is expected.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Sunday: Expect clouds to build through the day, with freezing levels reaching 2500m under light southerly winds. Monday & Tuesday: Continued clouds with light flurries possible. Winds remain light southerly and freezing levels may reach 1500m.
Avalanche Summary
We have reports of loose, moist avalanches being triggered by solar radiation on sunny slopes. A fatal avalanche incident occurred in this region on Wednesday. We will post more details when they become available.
Snowpack Summary
The warm temperatures have brought us into a spring melt freeze cycle with the surface snow softening with daytime warming on solar aspects then crusting overnight as temperatures dip back below freezing. On north aspects, the surface snow remains cold. Up to 60 of recent storm snow is settling quickly with the warm temperatures and this most recent storm interface is gaining strength. The early February surface hoar lingers, down 100-180cm. Although the avalanche activity has become more sporadic on this layer, triggering it would yield a very large destructive avalanche.
Problems
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.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.