Avalanche Forecast
Regions: Snoqualmie Pass.
Watch for new wind slab on non-traditional westerly aspects and small loose wet on solar aspects, especially as you increase in elevation and reach into the alpine Sunday.
Detailed Forecast
Moderate easterly winds at crest level and in the Passes should lessen Sunday afternoon. Temperatures will warm a few degrees over Saturday, especially in the alpine with high pressure moving into the region.
Watch for new wind slab on non-traditional westerly aspects especially as you increase in elevation and reach into the alpine where there has been more recent snow available for transport. E-NE winds should continue to build new wind slab Saturday night and Sunday morning. There may also be pockets of lingering wind slab on other aspects as well. Â
Small loose wet avalanches will be localized to steeper solar slopes near and above treeline and where wind effects are minimal.Â
Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow (new or existing) to pose an avalanche hazard.Â
Snowpack Discussion
Since the warm and wet start to February, fair weather through mid-February has lead to generally thick surface crusts and further consolidation of the snowpack, as well as further deterioration of the snow cover below treeline.
A few weather disturbances passed through in NW flow aloft the latter half of the week, bringing a welcome few inches of snow near and above treeline; the Paradise weather station recorded 8 inches over 2 days ending Saturday morning. Winds veered to the east or northeast on Saturday, causing some new wind slab formation on non-traditional westerly aspects mainly above treeline. Â
On Saturday, NWAC observer reports from the Crystal Mt backcountry described a few inches of new snow bonding well to the old surface and minimal wind transport through mid-day. However, at Winchester Mt in the Mt. Baker area, new wind slab 10 - 40 cm thick was observed above treeline on multiple aspects with new NE wind transport in progress. A small loose wet slide was triggered on a south slope late in the day even with the the cold temperatures and wind.  Â
The mid and lower snowpack west of the crest snow consists 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: South, South West, West, North West.
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, West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1