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Avalanche Forecast

Archived

Mar 19th, 2015–Mar 20th, 2015

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

Regions

Olympics.

Loose wet avalanches are unlikely but still possible, especially above treeline on slopes that have not already released. Also watch for isolated pockets of shallow wind slab on lee slopes above treeline. 

Detailed Forecast

An approaching frontal system should cause cloudy skies, moderate S-SW winds and periodic light rain and snow Friday in the Olympics.  

Loose wet avalanches are unlikely but still possible, especially above treeline on slopes that have not already released. Also watch for isolated pockets of shallow wind slab on lee slopes above treeline. 

Less recent snow and ample terrain anchors should greatly limit the avalanche danger below treeline. 

Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow to cause an avalanche danger.

Snowpack Discussion

Last weekend another warm and wet system brought a one-two punch to the Pacific Northwest. The initial system Saturday brought mostly rain with a few inches of snow at Hurricane. This was followed by a welcome 16-18 inches of new snow Sunday at the NWAC Hurricane Ridge station. A frontal boundary stalled over southern British Columbia brought persistent light rainfall to Hurricane Ridge on Thursday, with the snowline likely extending to 6500 feet or higher. 

NWAC observer Tyler Reid toured above Hurricane Ridge on Tuesday and reported about 1-2 feet of wet snow with up to 3 feet in drifts near ridges. There were numerous recent small loose wet avalanches seen on all aspects with a few larger avalanches. Avalanches ran into ares with little or now snow cover.

Loose wet avalanche debris size 2 on Tuesday, March 17th, above the tunnels on road to Hurricane Ridge. Photo by Tyler 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.

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.