New wind slabs may form overnight with light snowfall and moderate SW winds. Cornices may become weak with daytime heating and sun.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Saturday
Weather Forecast
A weak storm front is expected to reach the region Friday night. 5-10cm of snowfall is expected by midday Saturday. Alpine winds are expected to be moderate from the southwest and freezing levels are forecast to be around 1600m. A weak ridge of high pressure should dry things out Saturday night. A mix of sun and cloud is expected for Sunday with light to moderate alpine winds from the southwest and freezing levels around 1400m. The second storm front is expected to arrive Sunday evening and another 5-10cm is forecast for the overnight period. Dry and mostly cloudy conditions are currently forecast for Monday.
Avalanche Summary
On Thursday, several size 1 loose wet avalanches were reported from steep solar aspects. On Wednesday, a natural size 3 glide crack avalanche was reported. This released on the ground down 3 meters on a south aspect at 2000m. Explosive control trigger five cornice release size 1.5-2.5 on north through east aspects. None of these cornice releases triggered slabs. New winds slabs are expected to be the biggest concern on Saturday and cornices may become weak with daytime warming and sun.
Snowpack Summary
The new storm snow will bury a sun crust on south facing slopes and widespread surface hoar and/or facets everywhere else. New wind slabs are expected to form over the weekend with forecast moderate southwest winds in the alpine. The surface hoar and/or crust layer which was buried February 10 is now down 70-100cm but triggering this layer has become unlikely. Large cornices have recently been a concern but should also gain strength will colder temperatures.
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.