Avalanche Forecast
Regions: Olympics.
Detailed Forecast
Sunny weather with fairly warm temperatures should be seen Monday morning. High clouds should begin to move into the Northwest by Monday afternoon from an approaching frontal system.
This should not cause much change in the regional snowpack. Local storm or wind slab may linger on previous lee slopes mainly in the alpine. Watch for wind affected snow.
A photo from Saturday of wind affected snow at Hurricane Ridge from NWAC observer Tyler Reid.
Further small loose wet snow avalanches might be possible on steep solar aspects until the high clouds limit sun effects.
A weak front will begin to reach the area on Monday night and cross the Northwest on Tuesday.
Snowpack Discussion
A front crossed the Northwest Thursday afternoon and night. Temperatures began quite warm and cooled during the storm. This initially produced rain or wet snow that gradually turned to snow eventually reaching lower elevations. New snow amounts varied from north to south and with elevation. Upper elevations in the north received about 20-30 cm (8-12 inches) new snow with lower elevations and areas in the south getting about 10-20 cm (4-8 inches).
Sunny weather with warm temperatures is being seen this weekend.
Reports indicate mostly favorable profiles in the new snow and good bonding of the new snow to older wet snow. The mid and base pack mostly consists of stable layers of crusts and rounding or melt forms due to warm periods in late December.
But reports on Saturday show there is still some slab left out there from the recent storm. This is in the alpine where new snow amounts were heavier. A climber triggered a 1 foot storm or wind slab in the east facing bowl below Chair Peak near Snoqualmie Pass at about 5500'. Fortunately he stayed on top of the avalanche debris. It is interesting that there was an avalanche injury in about the same location about a year ago (see Accident Reports).
A photo of the Chair Peak slab crown.
A skier also triggered but was not caught by a 1-1.5 foot storm or wind slab on a south facing slope on Mt Herman near the Mt Baker ski area at about 5700 feet. The bonds here may not have been as good between the recent and old snow with the old crusted snow acting as a bed surface. Sunshine may have helped to activate this slope.
Small loose wet snow avalanches are also being reported on solar aspects this weekend.
There will be less danger in areas that received less recent snow such as Hurricane Ridge and Crystal Mountain. The avalanche danger will continue to be low at lower elevations due to less recent snow and a low snowpack.
Â
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: 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.
Aspects: South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1