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Avalanche Forecast

Archived

Feb 14th, 2016–Feb 15th, 2016

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

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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. 

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

Wind Slab avalanches are the 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.

Loose Wet

Loose Wet avalanches are the 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. 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.