Falling cornices continue to trigger large avalanches. Solar radiation and rapidly rising freezing levels make this a very real possibility on Sunday.
Weather Forecast
SUNDAY: Sunny. Light southeasterly ridgetop winds. Freezing level RAPIDLY RISING to 2000 m.MONDAY: Mix of sun and cloud with isolated flurries. Light southerly ridgetop winds. Freezing level hovering around 2000m.TUESDAY: Cloudy with flurries. Light southerly ridgetop winds. Freezing level around 1900m.
Avalanche Summary
A natural size 2 cornice failure that did not trigger a slab avalanche was reported in this region on Friday. The key weather factor to keep your eye on this weekend will be the sunshine accompanied by rising freezing levels. Solar radiation is a common trigger for cornices which is currently our primary concern.
Snowpack Summary
Cornices are large, looming, and the primary concern due to their potential to trigger large avalanches failing on facets at the bottom of the snowpack. Convective showers and moderate southwesterly winds have formed small wind slabs on lee features below alpine ridgetops. Solar radiation is a common trigger for loose wet avalanching in steep terrain, especially when new snow gets heated by the sun for the first time.
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.