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Avalanche Forecast

Archived

Mar 10th, 2014–Mar 11th, 2014

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

Regions

Olympics.

Increasing avalanche danger is expected Tuesday, especially during the afternoon on steeper slopes receiving direct sun.

Detailed Forecast

Light rain or snow showers should end Monday night with skies clearing.  Tuesday should be mostly sunny and start cool but warm rapidly, especially by midday and afternoon. 

The cooling through Tuesday morning should allow for shallow new crust formation near or at the surface helping to temporarily limit wet snow avalanches early Tuesday.  However, the near spring sun angles are gaining power and combined with rising freezing levels later Tuesday should increase the possibility of triggered wet loose avalanches especially on direct sun exposed slopes near and below treeline. Watch for pinwheels and surface wet snow deeper than a few inches.

There have been recent cornice failures the past few days at Hurricane and further natural or triggered cornice failures remain possible later Tuesday.  Avoid travel on or below cornices.

Small areas of new wind slab are possible above treeline at higher elevations, watch for signs of wind transported snow.

Snowpack Discussion

The past month has had 2 major storm cycles producing avalanche cycles in the Olympics and Cascades.

The first two week storm cycle ended February 25th and deposited about 9 feet of snow at Hurricane Ridge and caused numerous storm avalanches at Hurricane and across region.

The latest storm cycle wound down this past Sunday morning producing similar water equivalents as the February cycle.  Water equivalents and snowfall for the past week are about 4 inches and 2 feet for Hurricane Ridge.  This has been another period of rain and wet heavy snowfall and caused avalanches the past week at Hurricane and elsewhere in the Cascades.

More recent warm weather and rain this past weekend caused wet snow conditions, many wet loose avalanches on a variety of aspects both near and below tree line and caused several cornice collapses near tree line as reported by NWAC observer Katy Reid Sunday at Hurricane.

NWAC observers Tyler and Katie Reid on Friday reported wet and saturated upper snow pack layers but with no positive snow pit test results and numerous wet loose avalanches to size 2. Warming effects had penetrated quite deeply into upper snowpack layers.

Here is a video from Tyler and Katy at Hurricane on Friday.

Cooling Monday and a few showers are beginning to refreeze surface snow and form a new surface melt-freeze crust.  

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.