Storm slabs are expected to remain reactive, especially if the sun comes out on solar slopes and on wind loaded features in the alpine.
Confidence
Moderate - Timing of incoming weather systems is uncertain on Monday
Weather Forecast
SUNDAY: partly cloudy with flurries starting in the afternoon, up to 10cm expected overnight, moderate southwesterly winds, freezing level of 1200m. MONDAY: lingering flurries with sunny breaks, moderate northeast winds, freezing level of 1000m. TUESDAY: mainly sunny, light variable winds, freezing level of 1000m.
Avalanche Summary
Numerous natural and artificially triggered storm slab, windslab, and cornice avalanches have been reported in the last couple of days. Storm slab avalanches are expected to be remain reactive to human-triggering with ongoing snowfall and wind, especially if the sun pokes out. Cornices are reported to large and fragile, and may fail under the weight of a person.
Snowpack Summary
Up to 80 cm of settling storm snow overlies a thick rain crust which extends into the alpine. The snow is reported to be bonding well to the crust and all the recent avalanches have been failing within the recent storm snow, not on the crust interface. At treeline and below, other crusts may exist in the upper snowpack due to the recently fluctuating freezing levels. 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. The weak surface hoar layer from early January can be found down over a meter and is still reactive in isolated snowpack tests but triggering an avalanche on this layer has become 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.