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Avalanche Forecast

Archived

Feb 4th, 2016–Feb 5th, 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 possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

A mixed bag of ugly snow conditions and a considerable avalanche danger in the near and above treeline elevation bands is expected Friday. Careful snowpack evaluation will be needed on Friday.

Detailed Forecast

The next weather system will move strongly to the Olympics and north Cascades Friday late morning and spread to the rest of the Cascades by Friday evening with fairly high snow levels.

A broad brush will be applied to the avalanche forecast for Friday. Expect a mixed bag of ugly snow conditions and a considerable avalanche danger in the near and above treeline elevation bands at Hurricane Ridge.

Recent snow will be available for activation by rain and warm temperatures. Watch for surface wet snow deeper than a few inches and pinwheels or small natural loose wet avalanches that usually precede large loose wet avalanches.

Rain will load old wind slab and possibly cause wet slab avalanches in the near and above tree line bands.

But new snow and cooler temperatures should be seen by Saturday.

 

Snowpack Discussion

Heavy rain fell in the Olympics January 27th-28th with over 2 inches of rain recorded at the NWAC station at Hurricane Ridge.

The "20th of June" path released as a wet slab during the rain and warmth January 27th. Photo: January 29th by Matt Schonwald.

A strong occluded front with strong winds crossed the Northwest last Friday and Saturday. Hurricane Ridge had about 14 inches snowfall.

NWAC pro-observer, Matt Schonwald visited Hurricane on Friday, January 29th and found rapidly building wind slab and extensive loading on lee slopes in all 3 elevation bands. New cornices were sensitive to triggering but still relatively small. 

Cool, benign weather followed Sunday through Tuesday. A sun crust formed on many solar slopes and surface hoar was seen on many non-solar slopes.

A cold front crossed the Northwest on Wednesday. A warm front is causing more snow mainly in the south Cascades today. Hurricane Ridge for the 2 days ending Friday morning will probably have only about 4 inches increasing damp or wet snow.

 

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.

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.