Avalanche Forecast
Issued: Feb 14th, 2016 10:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Loose Wet.
NWAC,
Northwest Avalanche Center
The continued warm wet weather Monday will maintain wet snow conditions near and below treeline. New wind slabs and cornices should maintain dangerous avalanche conditions near and above treeline Monday.
Summary
Detailed Forecast
Moderate to heavy rain and snow is expected with strong winds and moderately high freezing levels Monday. The heaviest precipitation will shift from the southern WA Cascades Sunday night to the north WA Cascades Monday.
Many steep slopes may have released naturally by Monday due to warming and rain, locally lowering the danger on those slopes, however on slopes that have not released, natural or triggered avalanches should remain possible Monday.
Wind slabs should build on lee slopes below ridges at the higher elevations, Mainly N-SE facing near and above treeline.
Watch for fresh cornices along ridges and stay well clear.
Loose-wet avalanches will be a concern on steeper slopes at lower elevations. Watch for wet snow that gets deeper than a few inches.
Snowpack Discussion
Weather and Snowpack
The warmest weather of the winter occurred this past Sunday through Wednesday with extended temperatures climbing into the 50's in most areas, with some excursions into the 60's! Following a little light rain Thursday night, lowering snow levels and a pair of warm fronts brought new storm snow amounts of 8-16 inches from late Friday through Sunday morning.
The gradual cooling Friday changed rain to snow and caused a strong bond of new snow to the refreezing old wet snow surface as reported in the Mt Baker and Alpental areas Saturday. The upper snowpack should be well bonded to the 1/28 rain crust in all areas along the west slopes.
Significant warming Sunday combined with rainfall to cause wet snow avalanches on many steep slopes by early Sunday.
Recent Observations
Reports from the Mt Baker pro patrol Both Saturday and Sunday indicated the 14-16 inches of storm snow as of Saturday morning was reluctant to move during control missions both days. A few isolated wind slab pockets were noted along ridges, otherwise the warming Sunday afternoon was causing a few loose wet slides on steep slopes.
Reports from Stevens Pass Sunday indicated the 8-10 inches of storm snow became sensitive to ski triggers by late morning Sunday. These slides behaved as loose-wet avalanches as surface snow become increasingly wet.
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
Expected Size
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
Expected Size
Valid until: Feb 15th, 2016 10:00AM
