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Avalanche Forecast

Archived

Feb 27th, 2016–Feb 28th, 2016

Alpine
Natural avalanches unlikely, human triggered possible.
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

Olympics.

Mostly small, shallow areas of new wind and storm slab will be possible in the near and above treeline on Saturday. These avalanche problems would be greater if there is more new snow than expected. Watch for signs of loose wet avalanches mainly below treeline.

Detailed Forecast

Rain or snow should change to showers Friday night with lower snow levels. Partly cloudy weather Saturday morning should give way to some sun by Saturday afternoon at Hurricane.

This weather should bring a couple to a few inches of snow near and above treeline with a cooling trend. The cooling trend with rain changing to snow mainly in the near and above treeline should help bond new snow to previous snow.

New small areas of mostly shallow wind slab will be possible on isolated lee slopes. This should be mainly N to E slopes near and above treeline. Watch for firmer wind transported snow.

Small areas of shallow storm slab will also be possible if any areas receive a few inches of rapidly accumulating snowfall.

These avalanche problems would be greater if there is more new snow than expected.

Possible, mostly small, loose wet avalanches also will remain a problem in the below treeline on Saturday.

Snowpack Discussion

Weather and Snowpack

The last snowfall occurred late last week when about a foot of snow fell by last Saturday. Some cornices and wind slabs formed during this period but recent warm weather and sunshine have likely settled and stabilized wind slabs.

Springlike weather under high pressure Wednesday and Thursday caused abundant sunshine with temperatures climbing into the upper 40's Thursday afternoon. This weather has allowed for melt-freeze crust formation overnight and varying amounts of wet surface snow depending on slope aspect. 

Recent Observations

NWAC pro-observer Matt Schonwald was at Hurricane Ridge today Friday February 26th and found a pretty uniform stable snow pack due to warm weather. He generally found rounded grains and consolidated snow on solar slopes and moist snow on N slopes. A small area of possible wind slab was seen on a north slope called Lisa Jane near the visitor center but it was unsafe to test the slope. Clouds prevented the development of loose wet snow.

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.