As the weather clears, sun can destabilise cornices and recent storm snow.
Weather Forecast
An unsettled onshore flow is expected to bring lingering snow showers with a 1700 m freezing level and light NW winds on Friday. A ridge brings mixed sun and cloud through the weekend.
Avalanche Summary
Over the last week we have received many reports of cornice failure, including one that triggered what appears to be a size 3 persistent slab in the north Elk Valley.
Snowpack Summary
Large cornices overhang alpine slopes and threaten to trigger avalanches on slopes below. New storm slabs have developed in alpine terrain. Strong winds have also led to the development of new wind slabs. These overlie surfaces including crusts and old wind slabs. Deeply buried weak layers near the ground may remain sensitive to triggering from thin snowpack areas or with large loads such as cornice fall.
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.