Avalanche Forecast
Regions: Olympics.
In the Olympics, the main problem should shift to new areas of wind slab on lee wind exposed terrain, especially NE-N-E facing slopes.
Detailed Forecast
A brief break between storms is expected overnight Thursday with continued cooling. Another front should arrive Friday depositing moderate snowfall with shifting and increasing winds.Â
This weather should build new wind slab conditions on lee slopes, mainly NW-N-E facing slopes, especially below ridgelines near and above treeline.Â
Watch for cornice formation along ridges as well, avoiding slopes below.
Below treeline, the old wet snowpack should continue to drain, and refreeze forming a new crust. It may take awhile for the crust to become strong and supportive, so watch for areas of wet snow.Â
Snowpack Discussion
A strong front, moved across the Olympics Wednesday afternoon through Thursday morning, bringing heavy rain at high freezing levels. About 2 inches of rain were recorded at the Hurricane weather station as of Thursday afternoon. The snow line was at least to 7500 feet, well into the above treeline elevation band, likely saturating the upper snowpack, eliminating any near surface layers that may have existed.
Temperatures have cooled through the day Thursday with showery precipitation gradually changing rain to snow. This should allow for a favorable bond of new snow to the slowly refreezing, wet snow surface.Â
The main avalanche concern following this latest rain event should be new snow instabilities caused by newly forming wind slab or cornices. Mainly near or above treeline.
In the below treeline zone, wet snow conditions should gradually improve with continued cooling.Â
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Avalanche Problems
Wind Slabs
Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: North, North East, East, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1
Loose Wet
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. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. 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.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Elevations: Below Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1