Avalanche Forecast
Regions: Olympics.
Wind slab on lee aspects above treeline may still be sensitive to human triggering Tuesday. Wet loose concerns may become an issue mainly in the afternoon with gradual warming.
Detailed Forecast
Generally light rain and snow should glance the north Cascades and Olympics Tuesday.  New loading and wind transport is not expected to play a role in the avalanche danger Tuesday. Â
A modest warming Tuesday afternoon should lead to minor loose wet concerns on all aspects near and below treeline. Watch for loose wet concerns in the afternoon. Small point releases on steeper slopes have a fair bit of new and consolidated snow to entrain and would be the most problematic around terrain traps.  Storm slab avalanches should be unlikely given the generally good reports of bonding to the old snow surface and have been removed as a primary concern.Â
Generally soft wind slab at higher elevations may still be sensitive, and we advise the most caution when traveling at higher and more open avalanche terrain that may be wind loaded and where colder temperatures should preserve lingering instabilities.  Watch for cracking in the snow surface and for signs of obvious wind transport such as scoured lee ridges. Be aware that locally the soft wind slab concern may extend into the near treeline zone.Â
Snowpack Discussion
A stalled and moist frontal boundary draped over mainly the north WA Cascades Saturday afternoon finally sagged south on Sunday, with rain changing to snow generally in a north to south fashion across the PNW mountains.  A favorable temperature trend occurred with this storm, with gradual cooling from Saturday night through Sunday night.  From Saturday night through Monday morning Hurricane Ridge telemetry and NPS reports indicate about 18 inches of snow fell. Generally light showers at cool snow levels were seen through the day Monday, but moderate NW winds aloft likely transported snow Sunday night and continued into Monday.Â
Over the weekend NWAC observer Katy Reid reported a generally well consolidated lower snowpack NTL with moist snow from last week's periods of rain and warm temperatures reaching down into upper and mid snowpack.  Katy also reported new wind slab developing on lee easterly aspects near treeline Sunday afternoon, although no new avalanches were reported with this concern. A NPS park ranger at Hurricane Ridge reported a backcountry skier on Sunrise Ridge above the road Sunday afternoon was able to ski cut and release a storm slab about 15-20 ft wide that covered the uphill lane with debris. Fortunately the skier was not caught in the slide due to daytime warming creating unstable slab conditions.
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: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood: Likely
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