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Avalanche Forecast

Archived

Apr 12th, 2012–Apr 13th, 2012

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Coast.

Confidence

Fair - Freezing levels are uncertain for the entire period

Weather Forecast

Friday: Clouds and a few cm of snow, falling as rain below about 1400 m. Freezing level around 1600 m. Light northerly winds.Saturday: Cloudy with sunny breaks. Light, variable winds. Freezing level around 1500 m.Sunday: Warm, dry and cloudy. Freezing level rising to 1800-2000 m. Light winds, increasing from the SW by evening as a low pressure system approaches.

Avalanche Summary

Recent reports include cornice fall and loose wet avalanches. Full-depth size 2-3 glide avalanches have been releasing on rock slabs.

Snowpack Summary

Rain fell to 2000 m on Wednesday. Ongoing warm temperatures and the rain have caused the surface snowpack layers to become isothermal (at 0 °C), even on north aspects, to about 2100 m. This is expected to have formed a crust in some areas, now covered by a small amount of new snow. Very large cornices are looming. Glide cracks have opened up and pose the threat of large, full-depth releases, especially on steep rocky terrain features at low elevations. Otherwise, a relatively strong and deep spring snowpack exists, which becomes weak during periods of warm weather or rainfall. A buried crust/surface hoar layer from late March, within the upper 1.5 m of the snowpack, is reported to have gained strength in the Duffey Lake area, but remains a lingering concern.

Problems

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.