Confidence
Fair - Due to variable snowpack conditions
Weather Forecast
Monday: Light snowfall / Moderate to strong northwest winds / Freezing level at 1100mTuesday: Generally clear skies / Light southwest winds / Freezing level at 1300mWednesday: Moderate snowfall / Moderate southwest winds / Freezing level at 1500m
Avalanche Summary
No new natural activity was observed on Saturday; however, observations were somewhat limited. Having said that, numerous size 1.5 avalanches were triggered on various aspects between 2100m and 2300m by machines or by humans, one of which was remotely triggered from 10m away. In all cases the March 10 interface was the culprit. I would expect a new round of wind slab activity in response to new snow and wind on Saturday night.
Snowpack Summary
Generally moderate amounts of new snow fell on Saturday night and have have been distributed into deeper windslabs in lee terrain. These new accumulations overlie a deep and cohesive storm slab which formed last week with strong winds, very heavy snowfall and warm temperatures. This deep storm slab produced widespread and destructive avalanches in the region and may take some time to fully stabilize as it overlies weak surface hoar buried on March 10th. At lower elevations heavy rain penetrated the snowpack; however, subsequent cooling has helped strengthen the snow.Deeper weaknesses in the snowpack have now become unlikely to trigger.Widespread cornice development has also taken place, and cornices are reported to be very large and weak.
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.
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.