Regions
Northwest Coastal.
Weather Forecast
Wednesday: Continued light snowfall tapering off throughout the day, with freezing levels around 1000m, and moderate southerly winds. Thursday and Friday: A ridge of high pressure is expected to become anchored over the Pacific with dry conditions, light northerly winds, and daytime freezing levels around 500m.
Avalanche Summary
Reports from Monday include one relatively harmless but surprisingly deep (30-60cm) ski-cut wind slab on a steep rollover. Natural wind slab activity likely occurred Monday afternoon with strong to extreme southeasterly winds.
Snowpack Summary
15-40cm of new snow is bonding poorly to the previous snow surface, which includes surface hoar and/or a melt-freeze crust. Expect slabs to be particularly deep and touchy on wind-loaded slopes. Cornices are also very large and potentially unstable.
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.