Avalanche Forecast
Regions: Cascades - North West.
A transition from the recent wet warm weather to dry warm weather will begin on Tuesday. You will need to watch for a variety of snow and avalanche conditions on Tuesday.
Detailed Forecast
The upper ridge will begin to rebuild over the west US on Tuesday. This should cause light west winds with light showers mainly west of the crest decreasing Tuesday morning and ending Tuesday afternoon.
Wind slab from the past couple days may linger mainly on steep N to SE slopes near and above treeline. Watch for firmer wind transported snow especially in the above treeline of the south p[art.
New storm slab would be mainly in the south part from Monday where there is more than a few inches of snowfall in areas with light wind. This problem should be limited elsewhere due to limited new snow.
Any cooling will be limited Tuesday morning and temperatures will be on the rise again by Tuesday afternoon. More mostly small loose wet avalanches may be seen again below treeline Tuesday afternoon on steep mainly solar slopes.
As a result of the unseasonably low snowpack, especially at lower elevations, watch for terrain hazards such as open creeks, partially covered rocks and vegetation.
Snowpack Discussion
A series of fronts in an atmospheric river has been crossing the Northwest. The west slopes will have seen anywhere from about 3-14 inches of WE mostly as rain from about February 5th-10th with the most at Mt Baker. This caused another period of bad weather, instability, avalanches and poor skiing west of the crest. About 7-20 inches of melting, consolidation and stabilizing of the snowpack was also seen west of the crest.
At least some snow finally started accumulating above about 4500 feet in the north and 5500 feet in the south on Saturday.
NWAC pro-observer Jeff Hambelton was near the Mt Baker ski area Sunday and reported 7-10 inches of new snow near Artist Point about 5100 feet. Pit tests indicated the new snow was fairly well attached to the moist old snow surface. Of note were the numerous loose-wet avalanches releasing on most solar aspects entraining most of the new snow.
NWAC pro-observer Dallas Glass was at Stevens on Sunday and found 4-10 inches of moist or wet snow over the old snow surface. Recent snow was overall cohesive and well bonded. He triggered one small loose wet avalanche on a test slope.
NWAC pro-observer Jeremy Allyn was at Paradise on Sunday and reported a moist or wet stable upper snowpack.
A report via Turns All Year for Paradise on Sunday also indicated 1-3 inches of recent snow and pinwheels and natural point releases on solar slopes.
A filling low pressure system is crossing  mainly the south Cascades and Mt Hood area on Monday. This caused the most wind and rain or snow in the far south Cascades and at Mt Hood on Monday and Monday night. Lighter west winds and mostly light rain or snow showers were seen over the rest of the west slopes Monday night. A brief minor drop in snow levels should be seen mainly in the south Cascades and at Mt Hood Tuesday morning.
The mid and lower snowpack west of the crest should consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.
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, South East.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1
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.
Likelihood: Unlikely
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: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1