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Avalanche Forecast

Archived

Apr 11th, 2015–Apr 12th, 2015

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

Regions

Olympics.

Dangerous storm related avalanche hazards will generally be confined to the above treeline zone with enough of a snowpack to pose an avalanche threat. Watch for recent cornice formations along ridges and on slopes below especially during the warmest part of the day.  

Detailed Forecast

Showers should continue overnight Saturday, then end early Sunday with partial clearing expected. Freezing levels should remain low with moderate westerly ridgetop winds. This should continue to build areas of wind slab on lee slopes in the upper elevations as well as build cornices along ridges.  

Even with the winter-like temperatures, mid-April sunbreaks in the late morning or mid-day can trigger loose wet avalanches involving the new storm snow on solar aspects.  

Storm related avalanche hazards will mainly be confined to the above treeline zone or in near treeline locations with enough of a snowpack to pose an avalanche threat. 

Snowpack Discussion

Continued winter-like freezing levels and a frontal passage Friday night, followed by showers Saturday have deposited 8-10 inches of new snow as of Saturday afternoon. Moderate winds have likely transported new snow at higher elevations to build both wind slab and new cornices along ridges. In the Hurricane Ridge area, the recent new snow comprises just about the total snowpack and therefore limiting much increase in avalanche danger. No recent snowpack observations have been received from the Olympics since the new snow arrived through Saturday afternoon. 

Unfortunately, we are still a long way off from building a meaningful snowpack in the Olympic mountains as we head further into spring.   

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.