Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Friday: light to moderate precipitation starting Thursday evening and continuing throughout Friday morning / moderate southeasterly winds / freezing level at 1700m Saturday: cloudy skies with very light snowfall / light easterly winds / freezing level at 1700m Sunday: overcast skies with a possibility of clearing in the afternoon / light easterly winds / freezing level at 1900m
Avalanche Summary
On Wednesday and Thursday, numerous wet slab and wet loose snow avalanches to size 3 were reported in the region. They failed at all aspects and elevations bands, and occurred in response to very warm temperatures.With forecast weather, I expect a shift from wet snow avalanches to storm snow instabilities at higher elevations, while wet snow instabilities will still exist below treeline.
Snowpack Summary
Very warm temperatures have dominated the region in recent days and all but the highest, north-facing slopes saw moist to wet surface conditions. As of Thursday morning, slightly cooler temperatures have allowed light amounts of new snow to fall above about 2000m while rain continued to penetrate and weaken the snowpack at lower elevations. Up to 80cm below the surface, you might find remnants of facetted crystals sitting on a crust in the alpine and at treeline; however, I suspect that forecast cooling may assist in strengthening this weak layer in most areas. The mid-February buried surface hoar layer is down about 140-220 cm, although avalanches releasing on this layer represent a very low probability-high consequence scenario. Cornices in the region are very large. With spring temperatures, these are more likely to become weak and fail. They could provide a large enough trigger to release deep layers on slopes below.
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.
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.