Avalanche Forecast
Regions: Cascades - West.
Watch for locally sensitive wind slabs on lee slopes near and above treeline and sun affects on steeper solar slopes Wednesday afternoon.
Detailed Forecast
Freezing levels on Wednesday should continue the gradual rising trend that began on Tuesday. Increasing high and mid clouds should be seen in the afternoon. Recent storm snow should continue to settle, but filtered sunshine and increasing temperatures in the afternoon may activate loose wet avalanches predominately on steeper southerly slopes. Especially watch near and above treeline, where more snow is available for entrainment and could funnel you into a terrain trap. Â
Despite warming temperatures, there likely isn't enough new snow on southerly aspects below treeline for significant wet loose danger in the Snoqualmie area and southwest Cascades. Also, temperature inversions and easterly flow in the Cascade Passes will locally keep temperatures cooler.Â
Also, there may be pockets of sensitive wind slab mainly on N-SE aspects near and above treeline.
As a general backcountry travel safety note, tread carefully at lower elevations and on wind scoured aspects where terrain hazards (exposed rocks, trees, streams, etc.) are present.Â
Snowpack Discussion
Strong southwest flow carried a wet front across the Cascades Saturday night. This front tapped subtropical moisture which pushed snow levels high and resulted in 2-3 inches of rain for most NWAC sites west of the crest Saturday night. The exception was in the passes where Snoqualmie saw significant freezing rain and near Stevens Pass whom stayed mostly snow through early Sun AM.  Stevens saw the most skier and natural activity Sat night and Sun AM. Another half inch to 2 inches of water for the west slopes fell through Monday morning with snow levels hovering around 3000-3500 ft.  Â
The new snow on the backside of this storm Sun-Mon generally bonded well to the wet grains/rain crust along the west slopes or in the Snoqualmie area, a freezing rain crust. No significant avalanche activity was reported by professionals Monday or Tuesday outside of Stevens Pass.Â
Both Mon and Tue AM, pro-patrol at Stevens triggered 15-20" soft wind slabs on N-NE aspects of Cowboy Ridge, releasing down to the wet grains from early Sun morning mainly using explosives. A gaggle of NWAC pro-observers in Moonlight Bowl/Skyline area Tuesday of Stevens found wind transport on N-NE aspects near treeline but no wind slab. Storm layers reported by observers and on our observation page that failed in column tests were not likely to propagate.Â
Check out Monday's new videos from Dallas and Jeff H. on our YouTube Channel.Â
Below the most recent storm snow, the middle and lower snowpack should consist predominately of melt-freeze grains and crusts from warm stretches this winter. Â
Avalanche 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: South East, South, South West.
Elevations: All elevations.
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, South East.
Elevations: Alpine, Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1