Avalanche Forecast
Issued: Apr 9th, 2015 11:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet.
NWAC,
Northwest Avalanche Center
The main avalanche problem should be possible small loose wet avalanches on solar slopes. Use caution on slopes below cornices and on ridges where it can be hard to know if a cornice is present.
Summary
Detailed Forecast
An approaching Pacific frontal system should increase cloud cover along mainly the central and northeast Cascades Friday afternoon and cause a significant uptick in SW winds above treeline. Significant new snow and rain should hold off until Friday night across the east slopes.
The avalanche danger Friday should be limited to small loose wet avalanches on solar aspects and mainly above treeline.
It's April, so be aware of the increased sun effects reaching more aspects and affecting the snow surface fairly quickly. Loose wet avalanches involving shallow amounts of recent storm snow will be possible, especially in any direct sun on solar slopes earlier in the day.
Cornices won't be highlighted as an avalanche problem due to the cool weather but use caution on slopes below cornices and on ridges where it can be hard to know if a cornice is present.
Snowpack Discussion
A broad upper trough moved over the Northwest last weekend through early this week causing periods of very light snow east of the crest at low snow levels. On Wednesday and Thursday, clear skies transitioned to scattered afternoon showers with light and spotty new accumulations. April freezing levels have been very low compared to most of the winter, averaging about 4-5000 feet thus far.
A TAY report from Mt. Stuart Thursday had 6-12" of unconsolidated snow even on solar aspects above treeline, possibly a benefit from of the convergence zone from over a week ago.
Reports via TAY and from NWAC observer Jeremy Allyn around Washington Pass last weekend indicate shallow powder over crusts on north slopes, corn snow and crusts on solar slopes, and no signs of instability. Greater recent storm snow was being preserved west of Rainy Pass, where about 10 inches of great unconsolidated powder was seen on shaded terrain at higher elevations, providing a bit of welcome powder skiing!
Snowdepths vary greatly across the east slopes with a regionally healthy snowpack in the northeast Cascades to bare solar and lower elevation slopes in the central and southeast Cascades. Many areas at lower elevations and further away from the Cascade crest do not have enough snow to cause an avalanche danger.
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: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 10th, 2015 11:00AM
