Avalanche Forecast
Regions: Cascades - South West.
There may be some shallow storm and wind slab above treeline Monday. Any new snow that does fall will be susceptible to sun breaks later Monday afternoon, so use extra caution on steeper solar slopes near and above treeline.
Detailed Forecast
Light to moderate showers are expected as an upper trough passes Monday. Freezing levels should lower Monday, but be tapered by daytime warming.  Increasing SW ridge top winds may build shallow new wind slabs on some lee slopes, mainly below ridges on N-NE facing terrain near and above treeline.Â
Any new snow that does fall will be susceptible to sun breaks later Monday afternoon, so use extra caution on steeper solar slopes above treeline.Â
Less recent snow and ample terrain anchors should greatly limit the avalanche danger below treeline.Â
Remember the NWAC forecast applies to elevations up to the Cascade crest (~7000 to 8000 ft). Significant new snowfall from late this week likely posses a higher avalanche danger at these elevations in the Mt. Baker area which received the greatest recent precipitation.  Â
Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow to cause an avalanche danger.
Snowpack Discussion
The storm snow from last weekend has mostly settled or melted over the past week as snow depths have decreased about 10 inches where the greater storm snow accumulated, mainly the Mt Baker area.Â
The most recent new snowfall accumulated above 4000 feet in the Mt. Baker area Saturday with about 5 inches by early Sunday and 8-10 inches at about 5000 feet as reported by NWAC observer Jeff Hambelton, where there were some shallow loose wet slides seen on the north slopes of Table Mountain. No slab releases were seen with the new snow feeling moist, settled and mostly stable.Â
Less new snow accumulated in the remainder of the west slopes, however, there was widely varied amounts of precipitation so expect to find varied recent new snow amounts near and above treeline.  Â
The latest new snow was accompanied by moderate winds that built some shallow wind slabs and sensitive cornices along ridges, as observed by NWAC observer Jeremy Allyn in Silver Basin at Crystal Mountain, Saturday, March 21. There was a small natural cornice failure that triggered a shallow soft slab of about 4-6 inches. Daytime warming leading to consolidation.Â
The snowpack at low elevations remains meager to non-existent with the average snow-line around 4500 feet along the west slopes. 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: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
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, 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.
Aspects: South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1