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Avalanche Forecast

Archived

Mar 3rd, 2014–Mar 4th, 2014

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

Regions

Olympics.

Careful snow pack evaluation and caution will be necessary at Hurricane Ridge on Tuesday.

Detailed Forecast

Three day snowfall ending Tuesday morning should be about a foot at Hurricane Ridge. West southwest flow aloft should continue to carry warm front moisture to the Northwest. This should cause rain or snow showers with rising snow levels at Hurricane Ridge.

Wind slab will be a likely concern mainly on lee slopes at higher elevations. This should be mainly north to southeast aspects. Watch for signs of firmer wind transported snow.

Storm slab should also remain likely above the snow line on Tuesday on a wider variety of aspects. Wetter denser new snow accumulating over lower density snow will contribute to this concern.

Below the snow line wet loose avalanches will be the primary concern. Steep slopes that received heavy snowfall and then receive rain will be primed for wet-loose avalanches. Natural snowballing and smaller natural releases are usually precursors to this type of avalanche.

Snowpack Discussion

Recent Northwest Weather

A 2 week storm cycle ended a week ago causing about 9 feet of snowfall and avalanches at Hurricane Ridge.

Warm dry weather was seen late last week Wednesday to Saturday causing wet snow avalanches and melt/freeze crusts at Hurricane Ridge and throughout the region.

Observations for Hurricane Ridge area

NWAC observer Tyler Reid at Klahhane Ridge on Friday found plenty of wet unconsolidated snow on solar aspects below tree line. Some small surface hoar growth was noted in places. Here is his video from Friday.

On Saturday, a ranger and Tyler reported a very hard surface crust had formed as a result of the significantly colder overnight and early morning temperatures.

Another storm cycle began on Sunday and an avalanche cycle was likely at Hurricane Ridge as in the Cascades Sunday night and Monday morning although there are no observations to confirm at Hurricane Ridge. Poor bonds to the melf-freeze crust from late last week will likely have provided bed surfaces.

The mid and base pack around Hurricane Ridge still consists of stable crusts and melt form layers from periods of warm weather earlier this winter. But below tree-line zone on solar aspects rain and mild temperatures may keep the shallow snowpack wet and unconsolidated. 

Problems

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.

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.