Avalanche Forecast
Regions: Cascades - West.
Recent N-NE winds have created some wind slab on a variety of mainly southerly aspects, especially near ridges, so make sure to evaluate wind loaded terrain. Moderate avalanche danger means human triggered avalanches are possible! Watch for wet surface snow conditions on sun exposed slopes during the warmest part of the day
Detailed Forecast
Thursday should continue to be mostly sunny with light winds. Temperatures should remain warm. The main avalanche problem should be any areas of lingering wind slabs formed through Tuesday. More recent northerly winds likely redistributed snow on more southerly aspects above and near treeline. Warm temperatures and sunshine should again cause a chance of small wet loose slides on some steeper southerly facing slopes. good settled powder should persist on shaded slopes and wind protected slopes however.Â
Snowpack Discussion
A storm system finally hit the Northwest Saturday and Saturday night with a period of strong west to northwest winds. Most sites picked up about 12-20 inches of storm snow under a cooling trend. Lower total amounts fell at Snoqualmie Pass due to initially very wet snowfall.Â
High pressure over the past few days have produced, cool temperatures, sunshine and some strong east winds near the crest.
Most recent observations indicate storm snow instabilities have settled. Many exposed slopes have stiff wind affected snow surfaces, with some local wind slab formations, mainly ridges. In protected areas, well preserved low density surface snow is providing great conditions.Â
Example below of wind affected surface snow Wednesday on a NWAC/WSDOT  field trip to repair the weather station: D. D'Amico
Warming and sunshine Wednesday caused a few isolated wet loose slides and snowballing.Â
The main layering in the upper snowpack remains right side up with colder recent snow at the surface. Of course wind affected areas differ.
Strong mid and lower layers and well bonded rain crusts are preventing any deeper instabilities. However, there have been a few isolated field reports of persistent weak layers near older crusts, mainly in the Stevens Pass area, but no avalanche activity has occurred on these layers and they may be isolated in nature, but worth considering before attempting more consequential terrain.
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Avalanche Problems
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: South East, South, South West, 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.
Elevations: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1