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Avalanche Forecast

Archived

Apr 5th, 2014–Apr 6th, 2014

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

Regions

Olympics.

A continued mix of winter like and spring conditions should continue early Sunday with increasing wet snow conditions by Sunday afternoon. 

Detailed Forecast

Updated Sun AM to increase avalanche danger, especially storm slab near and above treeline and wet loose avalanche concerns lower in elevation.  Also, watch for and generally avoid weakened cornices along ridges. 

A front with increasing clouds and moisture will move across the region Saturday night, then east of the area Sunday. This is expected to cause increased winds and increasing rain and snow with slightly rising snow levels in the Olympics late Saturday and Saturday night.

This system should build some new shallow wind and storm slab at higher terrain and increase surface wet snow conditions below tree line.   

Watch for natural avalanches, pinwheels and surface wet snow deeper than a few inches on any solar slope Sunday.  Watch for evidence of wind transported snow in the higher terrain.

Snowpack Discussion

Only light amounts of about 4-6 inches of new snow have accumulated in the Hurricane Ridge area since last weekend.  Daily max temperatures have climbed above freezing most days, leaving a strong melt-freeze surface crust on most exposed slopes as of early Saturday morning. A park ranger from Hurricane reported a walkable surface crust Saturday morning with only very small amounts of new snow on the surface.

NWAC observer Katy Reid, reported Friday that all slopes had a melt-freeze crust with shaded terrain, maintaining 3-4 inches of soft and dryer recent snow being well bonded.  Heavier, moist to wet shallow surface snow was found on solar aspects with some shallow, loose wet slides, releasing on steeper exposed terrain by Friday afternoon.  Wind exposed terrain near and above treeline had been scoured of recent snow to firmer old surfaces. There were also some recent cornice growth noted as well as a few isolated, but stubborn wind pockets on lee slopes in higher terrain. 

 

 

Natural loose wet avalanche on 35 degree SW facing slope below tree line at Hurricane on Friday, April 4th. By NWAC observer Katy Reid.

Problems

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.

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.

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.