Avalanche Forecast
Regions: Cascades - South West.
Use caution in higher elevations where possibly greater new snow may accumulate, especially lee slopes near ridges. Watch for areas of wet snow at mid elevations, and during daytime warming.
Detailed Forecast
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A frontal passage Friday night should cause some light to moderate new snow, but initially rain changing to snow should leave good bonding of new snow to the old wet snow surface.Â
Watch for areas where new snow has been transported by wind to lee slopes at higher elevations along ridges. Also, watch for cornice development that may be soft and sensitive to trigger or release from daytime warming. Â
Less recent snow and ample terrain anchors may limit the avalanche danger below treeline. Many areas at the lowest elevations do not have enough snow to cause an avalanche danger.
Snowpack Discussion
Winter has been making a comeback in the PNW...now that it's technically spring. Though Thursday and Friday were definitely springlike with plenty of sunshine and temperatures climbing into the 50's and even 60's in most areas. Several systems moved through the region beginning last weekend, bringing 1-3 feet of storm snow and produced a few avalanche involvements.Â
A low pressure system moved east over the Mt Hood area Monday night/Tuesday morning and deposited new snow amounts west of the crest ranging from 3-5 inches from Mt Baker to Snoqualmie and from 8-12 inches from Crystal to Mt Hood. Small to large natural and skier triggered, loose wet and dry avalanches were reported at Alpental (TAY report), Crystal and Chinook backcountry Tuesday, the type depending on the time of day and aspect. Larger loose avalanches entrained snowfall from earlier in the week, and carried one skier in Powder Bowl at (closed) Crystal Mt.  NWAC observer Dallas Glass observed a remotely triggered storm slab near treeline above Paradise releasing within sensitive storm layers.
Steady warming, along with moderate precipitation brought more sensitive conditions to the Paradise backcountry again late Wednesday afternoon. Dallas reported small natural wind slabs on lee NE aspects near treeline in the morning transitioning to wet avalanche concerns with a switch to rain mid-day. Rain extended above 7000 feet late Wednesday and by Thursday morning above Paradise on Mt Rainier, there was evidence of a widespread large natural avalanche cycle.
Large natural slab release from 3/25 pm, Mt Rainier, Wilson Chute, east aspect ~ 7000 feet. Crown extended over 1 km along ridge! photo: Dallas GlassÂ
More natural avalanche evidence from rain event 3/25 Mt Rainier, east of McClure Rock, E aspect. Photo: Gary Vogt
Crystal and Chinook received far less loading, and professionals using explosives observed only localized loose and generally small avalanches.Â
Snowpack problems west of the crest for the time being should be in the upper or surface layers. The mid and lower snowpack west of the crest consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.
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: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
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