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Avalanche Forecast

Archived

Apr 15th, 2016–Apr 16th, 2016

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.

The amount of sun, heat and recent storm snow should be the main factors to consider on Saturday. More heat and more recent storm snow will generally mean more avalanche danger.

Detailed Forecast

An upper ridge and warm air mass should continue to build over the US west coast on Saturday with offshore surface flow developing over the Northwest. A warm front may clip the Olympics with some light rain or snow.

The amount of sun, heat and recent storm snow should be the main factors to consider on Saturday. More heat and more recent storm snow will generally mean more avalanche danger.

Small loose wet avalanches should be possible Saturday on steeper slopes involving snow received during the week. Watch for wet snow deeper than your boot tops, especially on steep solar slopes during the late morning to afternoon hours. But with increasing strong solar input all aspects could be affected even if skies are cloudy. Avoid areas below steep gullies and run out zones.

The potential for cornice releases will increase through the weekend. Cornice releases can be unpredictable during the spring so avoid areas below cornices and remember that cornices can break much further back than expected along ridges.

 

 

Snowpack Discussion

Weather and Snowpack

We've had two big warm-ups and spring shed cycles since the end of March. Over this time period the snowpack has undergone significant settlement with lower elevation snow beginning to fade away and with an overall transition to a spring snowpack.

A front crossed the Northwest Tuesday afternoon and night. Then a cool upper and surface low pressure system moved east along the Washington-Oregon border on Wednesday and Thursday. The NWAC Hurricane site indicated about 4 inches of late season snow ending Thursday morning and no more new snow ending Friday morning.

Storms in March continued to build unusually large cornices along many ridges. The potential for low probability/high consequence encounters, such as cornice failures and glide avalanches from steep unsupported slopes and smooth rock faces, should continue for awhile this spring. 

The mid and lower snowpack along the west slopes should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

No recent observations have been received from the Olympics.

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.