We are back to winter conditions for a short spell, heralding heightened avalanche danger. Moderate amounts of new snow will improve skiing, but will be strongly wind affected in exposed terrain.
Weather Forecast
Cool temperatures on Tuesday morning rise through the day, with SW winds increasing from Moderate to Strong. 5-10cm of snow is forecast for early Wednesday morning. Wednesday and Thursday should see flurries, Freezing Levels from valley floor to 1900m, and Moderate to Strong SW winds.
Snowpack Summary
Crusts and wind affect make for tricky skiing in places, but make for fast travel below treeline. New snow is being blown around by Strong SW winds, developing cornices on ridges, and wind slabs on many lee slopes. A crust-facet combo buried 40-70cm has strengthened somewhat, but has continues to produce sudden test results on some slopes.
Avalanche Summary
Fresh cornices on Forum Ridge on Sunday were reactive to human triggering, but only propagated a few meters. On Monday, a neighboring operation observed a large slab avalanche on a north aspect in the backcountry. It was naturally triggered in extreme terrain by cornice fall.
Confidence
Intensity of incoming weather systems is uncertain
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.