Avalanche Forecast
Regions: Cascades - North West.
A heightened avalanche danger will mainly be limited to steep open terrain or lee slopes above treeline, especially on the volcanoes where greater precipitation is expected.
Detailed Forecast
Warming is expected Monday with periods of light to moderate rain and snow with generally light to moderate winds. Rain near and below treeline should maintain some wet surface snow conditions, making triggered small loose wet avalanches possible on steeper slopes.
At the highest elevations, generally above 6000 feet, some building storm or wind slab is expected, especially on the volcanoes where more snow is expected. These areas of storm or wind slab may build on isolated terrain features, such as lee aspects near ridges, mainly NW through NE facing.Â
Do note as a result of the unseasonably low snowpack, especially at lower elevations, numerous terrain hazards such as open creeks, partially covered rocks and vegetation are widespread. Â
Snowpack Discussion
Another beat down of heavy rain over the past three days was somewhat redeemed Saturday, as snow levels lowered enough for snow to accumulate above about 4500 feet in the north and 5000 feet in the central and south.
In the Mt Baker area Sunday, observer Jeff HÂ reported there was, on average, 7-10 inches of new snow near Artist Point about 5100 feet. Pit tests indicated at that area, the new snow was fairly well attached to the moist old snow surface. Of note were the numerous loose-wet avalanches releasing on most solar aspects, entraining most of the new snow.
Small loose wet slides, involving about 4 inches of new snow, were being intentionally ski triggered by the patrol at the top of Crystal Mountain Saturday midday.Â
Warm temperatures with some sunshine during the day Sunday, have allowed any recent snow to settle and possibly melt, especially on solar aspects, helping to stabilize any new storm or wind slabs that may have formed above treeline Saturday.
The mid and lower snowpack west of the crest should consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.
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, North West.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 1
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: Alpine.
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