Avalanche Forecast

Archived

Feb 3rd, 2015–Feb 4th, 2015

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 possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

Snoqualmie Pass.

A mix of winter-like conditions above tree line and wet conditions mainly near and below treeline is expected on Wednesday.

Detailed Forecast

A weak warm front should lift south to north over the Northwest on Wednesday. Little if any rain or snow is indicated by the latest model runs during the daylight hours on Wednesday but there will be a warming trend.

Watch for possible leftover wind slab on steep lee slopes mainly above treeline. Surface hoar from the end of January could act as a weak layer where it survived and was buried intact.

Increasing wet loose avalanches is also possible on steep slopes. Watch for pinwheels and wet snow deeper than a few inches that usually precedes wet loose avalanches. This should be possible all steep slopes mainly near and below treeline.

An increasing avalanche danger should be seen starting Wednesday night and Thursday as the first in a series of wet and warm fronts moves to the Northwest.

Snowpack Discussion

The weekend of January 24th and 25th a warm and wet weather system caused high snow levels, rain, avalanches and extensive snowpack settlement.

Mild weather with sunny days or minor rain or snow was seen from about January 26th to about January 31st. This caused more consolidation, stabilizing and the formation of a thick strong stable surface crust in most areas. Surface hoar formed on shaded and north slopes in some areas in fair weather during this time.

Wetter weather from about February 1 through today has produced anywhere from about 0-10 inches of snow west of the crest with the most at higher elevations and in the Mt Baker area.

NWAC pro-observer Jeff Hambelton visited Artist Point next to the Mt Baker ski area February 2nd. Winds had redistributed recent snow which ranged from 0 to about 10 inches depending upon terrain and cross loading. He rated wind and storm slab layers as likely but an ECT did not indicate propagation.

NWAC pro-observer Jeff Ward was at Steven Pass on February 2nd where there was 4-6 inches of recent snow up to about 5800 feet. The main problem there was skier triggered wet loose avalanches on steep slopes of varied aspect.

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

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.

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.