Avalanche Forecast

Archived

Apr 7th, 2014–Apr 8th, 2014

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

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 and sensitive cornices again on Tuesday, human triggered avalanches will still be likely on steeper slopes.

Detailed Forecast

An approaching frontal system on Tuesday should spread increasing clouds and precipitation over the Olympics beginning in the morning and increasing during the afternoon. Southwest winds should increase in advance of the front. Snow levels will remain quite mild on Tuesday. Expect wet snow surface conditions and the possibility for wet loose avalanches to be enhanced during periods of moderate rain fall. Overall, increasing winds and cloud cover and cooler temperatures in the afternoon should lower the likelihood for wet loose avalanches a notch Tuesday, but remember the recipe for human triggered slides is still likely in the wrong terrain.

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.

Continue to be wary of cornices Tuesday and avoid traveling on slopes below them. Cornice failures are often seen during the transition to spring weather. Cornices have grown large recently and often break back further from the edge than expected.

Snowpack Discussion

A quick moving front Saturday afternoon and night brought rain to lower elevations and a wet 1-2" of snow to Hurricane Ridge with moderate south winds. A breakable crust reported by NPS rangers Sunday morning had turned to soft and heavy snow by Sunday afternoon with warming and clearing.

NWAC observer Katy Reid observed natural pinwheeling and rapidly increasing ski penetration in the wet surface snow Sunday afternoon. She generally reported shallow wet loose slides below treeline, but found one larger (D2) wet loose slide on a steeper NE aspect below treeline (see picture below). Digging around on different aspects near and below treeline, she found the moist upper snow (15-50 cm) overlying a hard melt-freeze crust to be un-reactive in snowpit tests. No reports were available Monday, but warmer temperatures and sunshine likely led to additional wet snow avalanches. Cornices have grown large over the last few weeks.

Wet loose avalanche near Maggie's Bowl, Hurricane Ridge, Katy Reid, 4-6-14

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.