Avalanche Forecast
Regions: Cascades - North West.
Moist to wet surface snow should gradually refreeze with light new snow accumulations expected by late Friday. Caution in higher elevations where possibly greater new snow may accumulate, especially lee slopes near ridges.
Detailed Forecast
Increasing clouds with initially very mild temperatures early Friday should gradually turn to light rain and snow by afternoon with gradually lowering freezing levels. A frontal passage Friday night should cause some new snow, but only light amounts are expected.Â
Strong melt freeze surface snow should gradually cool with some isolated and shallow wind or storm slabs developing by late Friday at higher elevations.Â
Recent fresh cornices along ridgelines may still be soft and reactive, likely being weakened by sunshine and warming Thursday. These should remain susceptible to failure Friday. Make sure to give them a wide berth, and be aware of corniced slopes above you.
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. The storm last weekend caused 1-2 feet of snow above treeline in the Mt Baker area. At the NWAC station at the base of the Mt Baker Ski Area there was about 8 inches of snowfall and there was up to a few inches elsewhere along the west slopes. On Sunday high on Heliotrope Ridge, a skier triggered and was partially buried by a 1-1.5 foot storm or wind slab avalanche.
A low pressure system moved east over the Mt Hood area Monday night/Tuesday morning and brought a taste of winter to the Cascades. New snow amounts west of the crest generally ranged from 3-5 inches from 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 in the 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 Thursday. 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 Thursday and by Friday 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 Rainer, Wilson Chute, east aspect ~ 7000 feet. Crown extended over 1 km along ridge! photo: Dallas GlassÂ
Another natural wind slab release from rain event 3/25 Mt Rainier on NE aspect, notice rain runnels. Photo: Dallas Glass
Crystal and Chinook received far less loading, and professionals using explosives observed only localized loose and generally small avalanches. No reports were received from areas further north Wednesday. 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
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: Possible
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.
Likelihood: Possible
Expected Size: 1 - 1