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Olympics

Issued: 7:48 PM PST Saturday, March 18, 2017
by Dennis D'Amico

NWAC avalanche forecasts apply to backcountry avalanche terrain in the Olympics, Washington Cascades and Mt Hood area. These forecasts do not apply to developed ski areas, avalanche terrain affecting highways and higher terrain on the volcanic peaks above the Cascade crest level.

The avalanche danger should decrease Sunday as a wet snowpack refreezes. Fresh but shallow wind slab will mostly likely be found above treeline. Shallow loose wet slides are likely on steeper solar aspects in the afternoon.

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Avalanche Problems for Sunday

Loose Weti

Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

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Wind Slabi

Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.

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Snowpack Analysis:

Weather and Snowpack 

The first week or so of March was very cool and snowy. NWAC stations along the west slopes of the Cascades and Olympics piled up about 3 to 8 ft of snow with the most at Mt Baker.

The 2nd week of March was equally active with non-stop Pacific frontal systems pummeling the PNW. Unfortunately these systems delivered far more rain than snow. At least two regional avalanche cycles occurred during the stretch. Significant snowpack consolidation occurred over this period due to rainfall and warmer temperatures. 

After a short respite from the active weather pattern on Thursday, another strong low pressure system brought several inches of rain to the west slopes of the Cascades and Olympics. Several inches of snow was seen early Friday night before continued warming pushed snow levels above Hurricane Ridge with moderate rain seen through early Saturday morning. Rapid cooling later Saturday morning was followed by generally light snow showers with little in the way of new snow accumulation. 

Recent Observations

NPS rangers at Hurricane Ridge reported about 5 inches of wet snow Saturday morning with little sign of recent wind transported snow. 

Detailed Forecast for Sunday:

Decreasing snow showers along with rapid cooling Saturday night through Sunday morning should transition to mostly sunny skies by Sunday afternoon. Freezing levels will be on the cool side Sunday but late March sunshine will help bump up temperatures to near or above freezing at lower and mid-elevations. Winds are forecast to be fairly light on Sunday.

The avalanche danger should decrease Sunday as a wet snowpack refreezes.

Generally small loose wet avalanches are likely at lower elevations and on solar slopes. Watch for surface wet snow deeper than a few inches, rollerballs or increasing small natural releases.

Fresh but shallow wind slabs have likely built on NW to SE aspects, mainly above treeline. Watch for firmer wind transported snow on other aspects, especially in areas of complex terrain.

Although the likelihood of wet slab or glides avalanches has greatly decreased with the cooling trend, these avalanche problems may still occur 24 to 48 hours following a heavy rain event. Continue to avoid unsupported slopes, especially where you know there is a smooth underlying surface or slopes with glide cracks. Wet slab or glide avalanches will not be listed as an avalanche problem in the Olympics due to less rainfall and increased cooling versus areas in the Cascades. 

It is always a good plan to travel well back from ridges, suspected of cornice formation, or on steep slopes below cornices.

No Corresponding Mountain Weather Forecast Available