Watch out for pockets of wind slab and give cornices a wide berth.
Confidence
Moderate - Freezing levels are uncertain on Wednesday
Weather Forecast
MONDAY: flurries overnight with up to 6cm expected, becoming mainly sunny through the day, light and variable winds, 1500m freezing level. TUESDAY: mainly sunny light southeasterly winds, 1500m freezing level. WEDNESDAY: mainly sunny, light westerly winds, 1500m freezing level with an inversion and above freezing level extending possible in the alpine.
Avalanche Summary
Numerous natural and artificially triggered storm slab avalanches have been reported in the last couple of days. Wind slab avalanches are expected to be remain reactive to human-triggering. Cornices are reported to large and fragile, and may fail under the weight of a person.
Snowpack Summary
Recent storm snow continues to settle and gain strength. Ongoing southeast through southwest winds have been loading leeward features in the alpine and large cornice development has been reported over the last few days. About 80cm of snow now sits on a thick rain crust that extends into the alpine. The overlying snow is reported to be bonding well to this crust. A weak surface hoar layer buried in early January can be found down over a meter deep. It is becoming increasingly hard to make this layer fail in snowpack tests and triggering an avalanche on it is unlikely.
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.