Avalanche Forecast
Regions: Stevens Pass.
Watch for wind slabs sensitive to human triggering on lee slopes near and above treeline and sun affects on steeper solar slopes Tuesday afternoon.
Detailed Forecast
Tuesday should be partly to mostly sunny with a gradual warming trend. Recent storm snow should continue to settle, but 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
Expect a higher regional likelihood of finding sensitive wind slab on N-SE aspects in the Stevens Pass area Tuesday. Approach wind-loaded slopes with caution and practice conservative decision making especially when pushing into the near/above treeline band. Â
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 Stevens Pass stayed mostly snow through early Sun AM.  Stevens saw the most skier and natural activity Sat night and Sun AM. Winds switched to westerly in the passes Sunday and a gradual cooling trend took place. 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 or in the Snoqualmie area, a freezing rain crust. No significant avalanche activity was reported by professional patrollers in the Baker or Alpental areas and while pro-observer Jeff H. near Church Mt found wind transport on north aspects near/above treeline, he did not find the new snow reactive.Â
Again, the most active area on Monday was Stevens Pass. Pro-patrol at Stevens triggered 15-20" soft wind slabs on N-NE aspects of Cowboy Ridge, releasing down to the wet layer from early Sun morning with ski cuts and explosives. Observer Dallas G. in the Skyline/Moonlight Bowl area Monday found less reactive storm layers in areas with less wind transport. The Stevens Pass avalanche danger rating will be higher and broken out from the other west slope zones.Â
Check out Monday's new videos from Dallas and Jeff H. on our YouTube Channel.Â
Below the most recent storm snow, the rest of the snowpack should consist 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: Likely
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: Possible
Expected Size: 1 - 1