Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
The big story for the forecast period is an intense frontal system lined-up to hit the South Coast on Monday night. WInds will be in the strong to extreme range with heavy snow accumulations. Tuesday: moderate snowfall tapering off around mid-day - moderate to strong southwest winds decreasing throughout the day - freezing level at 1100m Wednesday: very light snowfall - light southwest winds - freezing levels at 900m Thursday: Mix of sun and cloud as a clearing trend develops - light north winds - freezing level at 1100m
Avalanche Summary
On Sunday, ski cutting and explosives control produced numerous size 1-1.5 windslab avalanches that ran within snow that fell over the previous 24hrs. Expect widespread wind and storm slab avalanche activity with potential to step down to the deeper March 26 interface with weather forecast for Monday night.
Snowpack Summary
Light to moderate new snow accumulations have added to the 75-100cm that fell last week. Winds have mostly been moderate with strong gusts creating wind slabs on lee slopes. The past week's snow overlies reactive surfaces that were buried on March 26. This interface consists of a crust which exists on all aspects except true north facing slopes at treeline and in the alpine, where small surface hoar may be present in sheltered places. Below the March 26 interface, the snowpack is well settled and bonded. Cornices are huge, and will continue to grow with the forecast weather pattern.
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.
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.