Forecast warm temperatures, sunny skies, and high freezing levels are expected to weaken windslabs and cornices in the alpine.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Mix of high cloud and clear skies overnight with moderate southwest winds and freezing levels dropping down to about 1200 metres. Some warm air (slightly below freezing) may remain at higher elevations overnight. Tuesday mostly sunny with a chance of high cloud combined with light southwest winds and freezing levels rising up to about 2100 metres. Cloudy with light precipitation on Wednesday with moderate southwest winds and freezing levels around 1800 metres. Mix of sun and cloud on Thursday with light winds and 1600 metre freezing levels.
Avalanche Summary
Several cornice falls up to size 2.5 were reported on Monday. Continued strong westerly winds are developing windslabs on lee aspects.
Snowpack Summary
Roughly 5-10 cm of recent snow adds to the variable amounts of dry facetted snow on top of the mid-February crust with associated buried surface hoar in sheltered areas, or, more recent melt-freeze crusts on sun-exposed slopes. The late-Jan crust/surface hoar layer can be found about a metre below the surface in deeper snowpack areas. The mid-January surface hoar, can be found below that. These layers have gained significant strength, and chances of triggering these weaknesses have decreased dramatically. However, triggering may be possible with a large input such as cornice fall, or an avalanche stepping down, especially on slopes that see a lot of sun.
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.