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Avalanche Forecast

Archived

Apr 2nd, 2012–Apr 3rd, 2012

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast.

Confidence

Fair - Intensity of incoming weather is uncertain on Monday

Weather Forecast

The big story for the forecast period is an intense frontal system lined-up to hit the Coast on Monday night. WInds will be in the strong to extreme range with heavy snow accumulations. Tuesday: light snowfall - strong south winds decreasing to moderate throughout the day - freezing level at 1100m Wednesday: very light snowfall - light southwest winds - freezing levels at 1100m Thursday: Mix of sun and cloud as a clearing trend develops - light north winds - freezing level at 1200m

Avalanche Summary

On Sunday, numerous natural windslabs to size 1.5 were observed at treeline and above in the Duffey Lake area. With weather forecast for Monday night, expect widespread windslab and storm slab avalanche activity with potential to involve the deeper March 26th layer.

Snowpack Summary

Recent light snow accumulations add to the 40-70cm of snow that fell over the past week. Winds have mostly been moderate with strong gusts forming windslabs in lee locations. The past week's snowfall overlies an interface that was buried on March 26. This interface consists of a crust that exists on all aspects and elevations except north facing slopes at treeline and above where small surface hoar (5mm) may be found. The bonds between the new snow and the March 26th interface have been weak, especially in locations where the surface hoar is present. In the north of the region, persistent early February layers linger deeper in the snowpack and remain a concern with heavy triggers and rapid loading. Cornices are huge and potentially very destructive.

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.