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 - Intensity of incoming weather systems is uncertain on Tuesday
Weather Forecast
SUNDAY: partly cloudy with flurries starting in the afternoon, up to 5cm 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 800m.
Avalanche Summary
Isolated artificially and naturally triggered storm slab, wind slab and cornice avalanches continue to be reported. Storm slab avalanches are expected to be remain reactive to human-triggering with ongoing 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
40-80cm of settling storm snow overlies a thick melt-freeze crust which extends into the alpine. The snow is reported to be bonding well to the crust and 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. Freezing levels on Wednesday climbed to around 2000m and have to fallen to around 1400m. As the freezing level continues to drop, a crust is expected to form at lower elevations. 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. Although triggering this layer has become unlikely it is still reactive in isolated snowpack tests,
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.