Avalanche Forecast

Archived

Apr 10th, 2014–Apr 11th, 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 level shortwave should pass mainly into southern B.C. Friday, but this weather feature should grace the Olympics with variable cloud cover and perhaps an isolated shower. Temperatures should be near or slightly cooler than Thursday and winds should increase slightly in the afternoon.

The most extensive avalanche concern will be wet snow avalanches predominately on solar slopes Friday. 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 the recent failures, but they should be less likely to fail Friday. Still, avoid walking onto or below cornices - many have grown large recently. Cornices often break back further from the edge than expected and trigger avalanches on slopes below.

Snowpack Discussion

Fronts crossed the Northwest Friday and later Saturday. Water and snowfall for these systems at Hurricane was about .7 and 5 inches respectively. 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 by NWAC observer Katy Reid.

A weaker front moved east over the Northwest Tuesday afternoon and night. A weak short wave and colder air mass followed the front Tuesday night. No new reports are available today but more natural or triggered wet loose avalanches seem likely on solar slopes.

Below freezing temperatures Wednesday and Thursday morning at the Hurricane Ridge station have likely led to a firm melt freeze crust in the mornings and a decrease in wet loose concerns.

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.