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Mt Hood

Issued: 6:02 PM Tuesday, March 31, 2015
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.

 

Don't be fooled on April 1st by the escalating avalanche danger with elevation. Watch for sensitive slab avalanches involving new snow on lee easterly slopes near and above treeline as well as loose wet avalanches on solar slopes during sunbreaks and daytime warming Wednesday.

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Avalanche Problems

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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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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Storm Slabsi

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.

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Snowpack Analysis:

Winter made a bit of a comeback in the Northwest in mid to late March. Several storms or storm cycles brought heavy snow to the above treeline areas west of the crest especially on the volcanoes.

A vigorous front crossed the Northwest Friday night causing strong west-southwest winds along with some rain and snow. Snow levels lowered enough by Saturday to produce 2-3 inches of snowfall at higher NWAC stations west of the crest including at Mt Hood with likely a few more inches at higher elevations.

The Meadows patrol found some isolated shallow wind slab on Saturday on northeast slopes above 6500 feet. Mostly sunny and mild weather conditions were seen Sunday and Monday with no new avalanche problems reported. 

Snow levels fell quickly after a front moved through early Tuesday morning. Scattered snow showers through Tuesday afternoon had deposited several inches near and above treeline along with moderate westerly transport winds. In many areas the old moist surface should be slowly re-freezing with the new snow generally bonding well, keeping avalanche concerns confined to new storm snow layers.  

Detailed Forecast for Wednesday:

Additional light to moderate snow accumulations are expected Tuesday night through Wednesday at Mt. Hood. Moderate westerly transport winds are expected to continue through Wednesday. Showers may be locally intense Wednesday afternoon due to the unstable air mass over the region. 

Watch for sensitive slab avalanches involving new snow on lee easterly slopes near and above treeline as well as loose wet avalanches on solar slopes during sunbreaks and daytime warming Wednesday. Slabs may fail on graupel layers from Tuesday.

Cornices won't be listed as an avalanche problem but be aware of new cornice growth along ridgelines.

Snowpack problems west of the crest for the time being should be in the upper or surface layers. The mid and lower snowpack west of the crest consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter. Many areas at the lowest elevations do not have enough snow to cause an avalanche danger.