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Avalanche Forecast

Archived

Feb 14th, 2016–Feb 15th, 2016

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

Light to moderate rain and snow is expected with strong winds and moderately high freezing levels Monday. The greater precipitation will shift from the southern zones Sunday night to the north WA Cascades Monday. 

Some steep slopes may have released naturally by Monday due to warming and light 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

Two fair weather periods in January allowed surface hoar and near surface faceting to occur. These persistent weak layers were buried intact on Jan 3rd and 11th, but are no longer considered a persistent slab threat after several warm and wet systems tested this layer and it has been unreactive where it can still be identified in recent snowpit tests. A warm and wet system late last month caused a rain crust to form in most areas and elevations along the east slopes on Jan 28th. 

The warmest weather of the winter occurred this past Sunday through Wednesday with extended temperatures climbing into the 50's in most areas east of the crest. The warm temperatures and solar effects earlier in the week caused loose wet avalanches and overall snowpack consolidation, leaving behind a crust as temperatures cooled Friday.

A pair of warm fronts Thursday night through Sunday morning deposited about 6-12 inches of storm snow over most east slope locations, with the greatest amounts in the NE zone. 

Recent Observations

A professional observation from the northeast zone Saturday indicated that storm snow of about a foot remained cold and provided good ski conditions near and above treeline and was well bonded to the recent melt-freeze crust. Areas of wind slabs formed on some lee slopes below ridges due to moderate west wind transporting loose surface snow Friday night.

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.