Avalanche Forecast
Regions: Stevens Pass.
It's nearly spring and the sun's strength can rapidly create locally dangerous conditions on steeper solar slopes, where even a shallow and slow moving avalanche would be powerful and could force you into unintended terrain traps. Also, watch for weakening cornices along ridges during the warmer part of the day.
Detailed Forecast
A weak weather system Tuesday should cause cloudy conditions with light rain or snow at times. Only light amounts of new snow are expected and this should not cause a significant increase in danger.Â
Lighter snow accumulations along with 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 was received near and above these elevations on the volcanoes over the weekend and likely poses a higher avalanche hazard. 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 latest installment of warm and dry weather lasted from early to mid-March and led to more snowpack consolidation and a scarcity of avalanche activity.Â
Over the weekend, another warm and wet system in SW flow brought a one-two punch to the Pacific Northwest. The initial system Saturday brought 1.5 - 2.5 inches of rain with the snow line around 6000-7000 ft. On Sunday, a second low pressure system deposited about 8-16 inches above 6000 feet in the south Cascades and 4500 feet in the north Cascades by early Monday. Significantly lesser amounts of new snow were received below these elevations.  Â
NWAC observer Dallas Glass was at Paradise Sunday and observed a climber trigger a loose wet avalanche, size 2, on a steep slope at 6500 ft near treeline (no injuries). He found skier triggered moist storm slabs and loose wet avalanches were possible in the near treeline band involving the 8 inches (20 cm) of new storm snow.
Observations in the Mt Baker and Chinook Pass area Monday revealed some storm slab, natural avalanches that had released likely during the Sunday storm cycle.Â
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Evidence, Monday, March 16th of storm avalanche activity Sunday on Naches Peak, photo J. Stimberis
The snowpack at low elevations remains meager to non-existent with the average snow-line around 4500 ft 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
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: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1