Avalanche Forecast
Regions: Olympics.
Winter returned briefly to the Olympics over the weekend, but the mid March sun's strength can rapidly create locally dangerous conditions on steeper solar slopes, where even a shallow and slow moving avalanche could be powerful and could force you into unintended terrain traps. Also, watch for weakening cornices along ridges during the warmer part of the day.
Detailed Forecast
A weak weather system should cause a few showers overnight Tuesday and early Wednesday, but only very light amounts of rain or snow are expected and this should not cause an increased danger. Gradual clearing later Wednesday and some sunshone should lead to warming and increase the chance of small loose-wet avalanches.Â
Lighter snow accumulations along with ample terrain anchors should greatly limit the avalanche danger below treeline.Â
Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow to cause an avalanche danger.
Snowpack Discussion
The Olympics had very little snow until this weekend when a warm wet storm Saturday was followed by a strong but cooler storm Sunday for a one-two punch to the Pacific Northwest. Saturday's event brought mostly rain with a few inches of new snow by Sunday morning, followed by heavier snow depositing total storm snow amounts of about 16-18 inches at the Hurricane Ridge snow plot.Â
Observer Tyler Reid toured above Hurricane Ridge on Tuesday and reported about 1-2 feet of wet snow with up to 3 feet in wind drifts near ridgeline. There were numerous recent small loose wet avalanches seen on all aspects with a few larger slides.
Evidence seen Tuesday, March 17th, of size 2 loose wet slide debris above tunnels on road to Hurricane Ridge. Photo, Tyler Reid
Since many areas are starting from scratch, smooth slopes without terrain anchors or the slopes with the previous snow cover are the most likely to produce avalanches and most likely found near and above treeline in the Olympics.
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: All aspects.
Elevations: All elevations.
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: North, North East, North West.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 1