Avalanche Forecast
Regions: Cascades - East.
Avoid steep sun exposed terrain if you see wet snow deeper than a few inches and initial rollerballs or small loose wet avalanches that can indicate an increasing loose wet avalanche danger. Avoid travel on or below cornices. Wind slab may still be present near ridges above treeline in the Northeast zone.
Detailed Forecast
Light winds and sunny weather should be seen on Monday with moderately warmer temperatures.
Sunshine will melt and possibly cause loose wet snow avalanches on steep solar slopes. Avoid steep sun exposed terrain if you see wet snow deeper than a few inches and initial rollerballs or small loose wet avalanches that can indicate an increasing loose wet avalanche danger.
Past wind slabs should have mostly stabilized where formed on lee slopes, mainly above treeline and on NW-SE aspects, but will remain listed as an avalanche problem in the Northeast zone for higher terrain that received heavy storm snow Wednesday.
Recent cornices are very large. Natural cornice releases and resulting slab avalanches are dangerous and unpredictable. Give cornices a wide berth if traveling along ridge-lines and avoid slopes below large cornices. See a blog post regarding cornices here.
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Snowpack Discussion
Weather and Snowpack
March was wet and wild for weather and avalanches in the Cascades.
The last major system in March was seen Tuesday and Wednesday. Another 5-10 inches fell near the Cascade crest along with a warming trend and increasing W-SW alpine winds. Lesser amounts were seen further east of the crest and at lower elevations.Â
Cooling and showery weather Thursday allowed wet snow to begin refreezing with light amounts of new snow in most areas. The winds diminished Thursday and combined with daytime warming, this has allowed for wind slab and storm slab to begin stabilizing.
Very mild temperatures and increased solar radiation Friday allowed for wet surface snow conditions in most terrain, even northerly facing slopes.
A weak front crossed the Northwest on Saturday morning causing light rain mainly along the Cascade west slopes. This was followed by an upper trough on that caused some light amounts of snow along the Cascade west slopes at much cooler temperatures on Sunday. In most areas this will have refrozen upper layers of the snowpack.
Recent Observations
North
The NCMG were in the Cutthroat area on Monday 3/26 and found 15-20 cm of recent snow on a firm base. Loose wet avalanches and cornices were the main concerns.Â
On Tuesday 2/27, the NCMG in the Highway 20 Hairpin area found that ski and hand tests indicated good bonds of recent snow to previous snow. Loose wet avalanches were the main concern at lower elevations. Touchy or stubborn wind and storm slab, and cornices were still expected near and above treeline.
A public observation from the Washington Pass area on Tuesday 3/27 reported small ski triggered 10 in wind or storm slab on steep E slopes near a ridge line.
Central
No recent observations.Â
South
No recent observations.Â
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, Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1