Avalanche Forecast
Regions: Cascades - South West.
Due to the showery weather pattern, a wide variation may exist in new snow amounts. The moderate hazard rating will be maintained near and above treeline across the Cascades for new storm snow problems, but watch for areas with greater new snow as having a potentially higher local danger.
Detailed Forecast
A slowly changing weather pattern will maintain cool weather, light winds and isolated showers again Tuesday.  Only light amounts of new snow are expected Monday night through Tuesday.  Due to the showery nature of the expected precipitation, a fair amount of uncertainty is expected with the subsequent hazard forecast. A moderate hazard rating will be maintained near and above treeline across the Cascades for any new storm snow problems. However, in areas that receive little new snowfall through Tuesday afternoon... expect a lower avalanche danger than the regional forecast.Â
Shallow storm slabs may develop Tuesday in areas that receive greater shower activity. It's April, so be aware of the increased solar input reaching more aspects and affecting the snow surface quickly. Loose wet avalanches involving shallow amounts of recent storm snow will be also be possible Tuesday, especially during sunbreaks in the afternoon.Â
Small loose dry avalanches are also possible for non-solar aspects at higher elevations. Loose dry avalanches won't be listed as a top avalanche problem, but be aware of fast moving sluffs knocking you off your feet and into unintended terrain traps on steeper slopes.Â
Due to the continued cool weather, cornices won't be highlighted as an avalanche problem either, but use caution on slopes below cornices and on ridges where it can be hard to know if a cornice is present.
Snowpack Discussion
Periods of active weather and mountain snowfall have finally graced the PNW since about mid March onward, and led to a few natural avalanche cycles.Â
A front moved across the Northwest last Tuesday, followed by showers and rapid cooling. Storm snow from this system ranged from about 3-10 inches along the west slopes except at Snoqualmie Pass where 15-20 inches fell Tuesday night. A small natural cycle occurred at Alpental likely during heavy loading early Wednesday, but overall the new snow came with little avalanche activity. A front on Friday night brought another 1-4 inches across the west slopes, with an additional trace to a few inches in showers over the weekend.Â
The average freezing levels in April have taken a major dive compared to much of this winter, averaging between 3-4000 ft since April 1st. This has helped feed the backcountry reports from across the Cascades near and above treeline of cool, preserved snow on non-solar aspects with limited wind effects, along with gradual storm snow settlement and generally a good bond to the previous crust.  On solar aspects, sun breaks even during low freezing levels have caused generally small loose wet avalanches. Sun crusts may now be found on solar aspects. Rather large cornices continue to be reported along ridges, especially in the north zone.
Snowpack problems west of the crest should remain 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 season. Many areas at lower elevations do not have enough snow to cause an avalanche danger.
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