Avalanche Forecast
Regions: Olympics.
Avoid avalanche terrain Monday especially at higher elevations.
Detailed Forecast
Another weather disturbance passing through Monday will bring another round of wind and light to moderate rain and snow to the Olympics. Snow levels are expected to oscillate around 4000 feet on Monday.Â
New unstable storm layers from Sunday night and Monday should be found near or just below treeline with unstable slabs forming on open lee terrain near and above treeline. Avoid steep open slopes, slopes connected to steep open slopes above and lee slopes receiving wind deposited snow.Â
Wet loose avalanches will be likely on steeper rain soaked slopes...and may entrain snow down to the crust from last week. Â
Also watch for recently formed large cornices along ridges and give them a wide birth and safety margin. They may be weakened by the warmer temperatures and new loading. Â
Snowpack Discussion
Recent Northwest Weather
An extended mild and dry period occurred the latter half of January generally forming a crust in all areas. Very cold weather followed in early February which produced light low density snowfall, near surface faceting, and faceting near and just above the crust.
An extended 2 week storm cycle wrapped last Monday night, capping off impressive amounts of some 6-7 feet of new snow with a rain event that reached to near 7000 feet in the Olympics. Much of the following week saw sunshine and some very mild temperatures Tuesday through Thursday. Colder air arrived Saturday along with gradually increasing ENE winds.  A stronger frontal system with increasing temperatures and wind was in progress Sunday afternoon. Significant snowpack settlement occurred through the week during the warm stretch.
Observations for Hurricane Ridge area
Following the storm cycle, the deep cold snow layers took a dramatic turn Monday in the near and below tree line zones as rain returned and fell through Monday night and quickly changed the recent low density dry snow to wet snow conditions.   Runnels were reported on a variety of aspects and elevations following the rain event. There were many field reports in  the Hurricane Ridge area Tuesday through Friday giving evidence of widespread wet snow avalanches running on most steeper slopes and a variety of aspects.Â
The latest observation on Friday, Feb 28th by NWAC pro observer Tyler Reid comes from Klahhane Ridge to the east of Hurricane where plenty of wet unconsolidated snow was found on solar aspects below tree line from 4400-5600 feet.  Some small surface hoar growth was noted in places. For pre-storm conditions from the area see this video from Friday.
On Saturday, NPS ranger and Tyler reported a very hard surface crust had formed as a result of the significantly colder overnight and early morning temperatures. New snow received Sunday afternoon may not be bonding well to this layer.Â
The late January crust layer and associated weak layers of early February are now deeply buried by the storm cycle snow.  While they were producing areas of collapsing and large whumpfing in mid-late February, they have not been involved in any recent avalanche activity. While triggering a slide on this layer has become unlikely, we are still urging more conservative travel plans based on the premise that not enough information is known about this layer and a slide on that layer could be devastating. This will not be listed as an avalanche concern while more likely storm related concerns are present.Â
The mid and base pack around the Hurricane Ridge area still consists of stable crusts and melt form layers from periods of warm weather earlier this winter. The exception will be in the below tree-line zone on solar aspects where rain and mild temperatures keep the shallow snowpack wet and unconsolidated.Â
Avalanche Problems
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
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, East, South 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: Likely
Expected Size: 1 - 1