Lingering storm slabs and cornices are expected to become weak with sun exposure and afternoon warming. Use extra caution on sun exposed slopes when the solar radiation is strong.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
Unsettled conditions are expected for Wednesday as a ridge of high pressure builds over the coast. Cloudy conditions with light flurries are expected for the morning and a mix of sun and cloud is expected for the afternoon. Afternoon freezing levels are expected to be around 1200m and alpine winds are forecast to be moderate from the northwest. Sunny conditions are expected for Thursday with afternoon freezing levels around 1500m and light to moderate outflow winds. A mix of sun and cloud is forecast for Friday with freezing levels climbing to around 2000m and moderate southerly winds in the alpine.
Avalanche Summary
On Monday, a natural size 2 cornice release was reported but did not trigger a slab. Ski cutting was produced size 1 wind slabs 10-30cm thick. Natural and artificially triggered avalanche activity up to size 2.5 was reported from across the region over the weekend. In the north of the region on Sunday, a cornice collapse triggered a size 3.5 deep slab avalanche which failed on glacier ice. If the sun comes out on Wednesday, cornices and lingering slabs are expected to become weak, and could even fail naturally. Loose sluffing is expected from steep sun exposed slopes.
Snowpack Summary
Up to 75cm of snow fell over the last week. This snow is reported to be settling and gaining strength, but lingering storm instabilities may still exist, especially in recently wind loaded terrain features. Cornices are reported to be large and fragile. Isolated sun crusts can already be found on steep sun exposed slopes, with widespread sun crust formation expected in the next couple days. The mid and lower snowpack are generally strong and well-settled. Below 1200m the snowpack is reported to be isothermal.
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 Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.