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Avalanche Forecast

Archived

Mar 2nd, 2017–Mar 3rd, 2017

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Very dangerous avalanche conditions are expected to develop especially near and above treeline Friday due to an incoming storm system. Travel in avalanche terrain is not recommended due to the increasing hazard. 

Detailed Forecast

Several waves of warm frontal moisture will impact the Olympics Thursday night through mid-day Friday. A strong cold front will sweep through the area early in the afternoon. The warming trend should peak early afternoon for the Olympics.  

Rain will creep higher in the below treeline band late Thursday night through Friday morning for the Olympics before snow levels begin to fall in the afternoon. Moderate to strong southwest winds will increase Thursday night and stay elevated through Friday afternoon.   

Very dangerous avalanche conditions are expected to develop especially near and above treeline Friday due to an incoming storm system. Travel in avalanche terrain is not recommended due to the increasing hazard. 

Storm slab should build and become more reactive late Thursday night through mid-day Friday day due to the warming trend.  

Wind slab will build on lee easterly aspects near and above treeline, but expect cross-loading and wind slab formation into the upper portion of the below treeline band due to the strength and duration of the winds.  

Generally shallow loose wet avalanches are likely below treeline. 

Snowpack Discussion

Weather and Snowpack

The most recent wet warm storm arrived on Valentines Day 2/14 and formed the uppermost, very strong rain crust in the snowpack. 

A series of disturbances in cool, NW flow aloft from Saturday through Tuesday caused periods of moderate to strong S-SW-W alpine winds at Hurricane. The 4 day storm snow amounts over this period were about 10 inches at Hurricane Ridge.

The NPS ranger at Hurricane Ridge reported 4 inches of new snow Thursday morning with south winds increasing to 10 to 20 mph. 

Recent Observations

No observations have been received from the Olympics in the past several days.

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.