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Avalanche Forecast

Archived

Feb 10th, 2015–Feb 11th, 2015

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

Stevens Pass.

The primary concern Wednesday should be loose wet snow avalanches.

Detailed Forecast

Fair weather should be seen on Wednesday with some high clouds especially over the Olympics and north Cascades. Quite a rise in freezing levels should be seen Wednesday so that means significantly warmer temperatures.

The main problem on Wednesday west of the crest should be loose wet avalanches. Watch for natural or triggered rollerballs that would initially be see on steep solar slopes but that could spread to other slopes. Don't underestimate the power of slow moving loose wet snow avalanches which could take you some where you don't want to go such as into gullies or other terrain traps and then sets up like concrete. These conditions should extend to some extent down into the near treeline and the upper part of the below treeline.

Lingering wind slab will be listed as a problem for one more day west of the crest above tree line. Watch for firmer wind transported snow on previous lee slopes mainly on N-SE slopes near ridges.

As a result of the overall low snowpack, especially in the lower part of the below tree line, watch for terrain hazards such as open creeks, partially covered rocks and vegetation.

Snowpack Discussion

A series of fronts in an atmospheric river crossed the Northwest the past few days. NWAC sites along the west slopes saw anywhere from about 3-14 inches of WE mostly as rain with the most at Baker. What a winter we are having in the Northwest! This caused another period of bad weather, instability, avalanches and poor skiing west of the crest. About 7-20 inches of melting, consolidation and stabilizing of the total snowpack was also seen at NWAC sites west of the crest.

About 5-12 inches of heavy snow was seen above treeline the past couple days west of the crest based on weather station data and reports.

NWAC pro-observer Dallas Glass was on a lee slope near the top of Crystal Mountain ski area today. He reported 12 inches of recent snow and easily triggered roller balls up to 2 feet with little sign of slab layers in the heavy snow. So the snow there was already starting to get ripe today.

The mid and lower snowpack west of the crest should consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

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.