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Avalanche Forecast

Archived

Mar 29th, 2015–Mar 30th, 2015

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

Regions

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Less recent snow and rain has given the snowpack east of the crest a chance to partly consolidate and mostly stabilize.

Detailed Forecast

Frontal moisture should mostly lift north to BC  Sunday night to Monday afternoon. Fair weather is expected east of the crest.

Past snow has had a chance to partly consolidate and mostly stabilize east of the crest. Possible loose wet avalanches should be the main problem and will be emphasized on solar slopes but watch for loose wet conditions on all aspects.

Older wind slab may linger on previous lee slopes. Watch for possible firmer previously wind transported snow mainly on north to east aspects.

Cornices won't be listed as an avalanche problem. But avoid slopes below cornices and ridges or summits where cornices may be hard to see in all areas.

Snowpack Discussion

The 1-2 feet of snow that fell in mid-march east of the crest, mainly in the northeast Cascades, has settled or melted and likely been absorbed into the upper snowpack. 

The DOT crew working at Washington Pass early last week reported mostly stable overall snow conditions with 4-6 inches of recent snow above the pass and about 2 inches at pass level. One natural loose dry avalanche was seen at about 6500 feet on Silver Star Peak on Tuesday.

A warm front caused only light amounts of rain and snow east of the crest Wednesday to Thursday morning with gradual warming along the east slopes. NWAC Observer Tom Curtis was on Nason Ridge on Thursday and reported small to medium rollerballs and evidence of recent small to large loose wet avalanches.

A front and short wave crossed the Northwest Friday night causing strong west-southwest winds, some rain and snow and lowering snow levels. But rain and snow amounts were light east of the crest.

Frontal moisture is moving mainly to BC Sunday. But fair weather is generally being seen east of the crest.

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.