Avalanche Forecast

Archived

Apr 11th, 2014–Apr 12th, 2014

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Watch for wet loose concerns mainly during the afternoon and on steeper solar slopes.

Detailed Forecast

A weak upper trough is passing across the north part of the forecast area Friday night and will pass east of the area Saturday. Only a chance of a little precipitation is expected with a little cooling by early Saturday. This should keep temperatures cooler Saturday and limit melting and thus limit the extent of wet snow avalanche potential Saturday.

The primary avalanche concern will be wet snow avalanches predominately on solar slopes Saturday. Watch for wet surface snow deeper than a few inches, roller balls in surface snow and small natural wet loose releases that usually precede more major wet loose snow avalanches. Avoid terrain traps where a small but powerful wet loose avalanche could have unintended consequences.

Cornices will be listed as a secondary concern due to some recent failures, but they should be less likely to fail Saturday. However, continue safe travel techniques by avoiding walking onto or below cornices - many have grown large recently. Cornices often break back further from the edge than expected and can trigger avalanches on the slopes below.

Snowpack Discussion

A pair of weak fronts crossed the Northwest a week ago Friday and later Saturday, depositing about 5 inches of snow at Hurricane Ridge. Warm temperatures were seen by Sunday and especially Monday.

NWAC observer Katy Reid observed increasingly wet surface snow Sunday afternoon. She reported shallow wet loose avalanches below treeline, but found one larger (D2) wet loose avalanche on a steeper NE aspect below treeline (see picture below). No reports were available Monday, but warmer temperatures and sunshine likely led to additional wet snow avalanches.

Wet loose avalanche near Maggie's Bowl at Hurricane Ridge on Sunday, April 6th by NWAC observer Katy Reid.

Subfreezing temperatures Wednesday through Friday morning and daytime highs in the 40's at the Hurricane Ridge station have likely formed a firm melt freeze crust for the mornings and shallow wet snow conditions by the afternoon hours.

Problems

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.

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.