Avalanche Forecast
Regions: Olympics.
Warmth and the late March sun will focus the avalanche hazard on wet snow concerns Wednesday. High freezing levels, light winds and sunny skies over the next several days will cause natural loose wet avalanches on solar aspects and increase the odds for low likelihood/high consequence problems such as cornice failures.
Detailed Forecast
On Wednesday, freezing levels should rise to near or above 10000 feet in the Olympics. Warmth and the late March sun will focus the avalanche hazard on wet snow concerns Wednesday. High freezing levels, light winds and sunny skies over the next several days will cause natural loose wet avalanches on solar aspects and increase the odds for low likelihood/high consequence problems such as cornice failures.
Melt-freeze crusts can quickly break down with intense spring sunshine. In areas that have received more recent snowfall, small loose wet avalanches have the potential to entrain deeper layers. Be aware of terrain traps where even a small loose wet avalanche could have unintended consequences. Plan to avoid steep solar slopes by late morning/mid-day to minimize the problem.  Â
In isolated areas above treeline, a mix of older wind slab on lee easterly aspects and newer wind slab on south through westerly aspects will maintain wind slab potential on a variety of aspects. Watch for cracking and firmer or chalky wind transported snow.  Â
Many areas have large cornices along ridge-lines so be cognizant of the hazard above. Unlike the loose wet problem, you may not have much notice that a cornice is about to fail. Cornices can break much further back on ridges than expected and releases can be unpredictable during the spring.
Snowpack Discussion
Weather and Snowpack
Snow accumulations Wednesday 3/23 to Friday 3/25 were about 4-6 inches at Hurricane with new snow of over a foot on wind loaded slopes near treeline. This snow bonded well to a moist crust buried March 22nd.
A strong front crossed the Northwest Sunday morning followed by a large upper trough and a cool unstable air mass Sunday afternoon and evening. Snowfall accumulations were lighter in the Olympics than the west slopes of the Cascades, with only a few inches of new snow likely through Sunday night.Â
Hurricane Ridge pushed to 40 degrees early Tuesday afternoon under mostly sunny skies.Â
Frequent March storms have built large cornices along some ridges in the Hurricane Ridge area.
The mid and lower snowpack in the Olympics should generally be a stable mix of crusts and layers of moist and rounded snow crystals.
Recent Observations
NWAC professional observer Matt Schonwald toured in the Hurricane Ridge area Friday 3/25.  Matt generally found the new storm snow unreactive in snowpit tests and with ski cuts on test slopes. No recent avalanches were observed in the Hurricane Ridge area. Wind effects were limited to directly below ridgelines, with generally settled powder and good skiing found on non-solar aspects with less wind effect. Area cornices were firm and unlikely to trigger.
The road to Hurricane Ridge was closed on Sunday. But the Park Service reported that hikers heard natural avalanches in the vicinity of Lake Angeles a few miles northeast of Hurricane. Details were not available due in part to low visibility.
Avalanche Problems
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.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1 - 1
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 lips 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.
Cornices can never be trusted and avoiding them is necessary for safe backcountry travel. Stay well back from ridgeline areas with cornices. They often overhang the ridge edge can be triggered remotely. Avoid areas underneath cornices. Even small Cornice Fall can trigger a larger avalanche and large Cornice Fall can easily crush a human. Periods of significant temperature warm-up are times to be particularly aware.
A corniced ridgeline. A large cornice has formed at the top of the ridge. A smaller cornice has formed to the left of the trees from crossloading.
Cornices are easy to identify and are confined to lee and cross-loaded ridges, sub-ridges, and sharp convexities. They are easiest to trigger during periods of rapid growth (new snow and wind), rapid warming, and during rain-on-snow events. Cornices often catch people by surprise when they break farther back onto flatter areas than expected.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1
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: All aspects.
Elevations: Alpine.
Likelihood: Unlikely
Expected Size: 1 - 1