Mt Hood

Issued: 6:00 PM Sunday, March 1, 2015
by Kenny Kramer

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.

Some strong N-NE winds later Monday may transport any available surface snow to more unconventional southerly facing slopes. 

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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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Snowpack Analysis:

A wet start to February was followed by mostly fair weather through mid-February, leading to generally thick surface crusts, as well as further deterioration of the snow cover below treeline. Weak weather disturbances last week produced light snowfall, but no new avalanche concerns. 

New snowfall at NWAC Mt. Hood stations from Wednesday night through Thursday afternoon ranged from less than 1 inch at Meadows to a soggy 3 inches at Timberline with likely higher accumulations and some loading of easterly aspects above treeline. 

On Friday and Friday night, Timberline received roughly 6 inches of new snow, with about 4 inches at Mt. Hood Meadows. Still, this was enough to build sensitive new wind slab Friday morning at about 6600 ft on a NE aspect at Meadows, with soft wind slabs around 1 ft easily releasing. 

The winds shifted and became very strong from the E-NE Friday night and Saturday, especially above about 6500 feet where much of the recent surface snow has likely been stripped from most slopes. The winds were so strong to likely have blasted the shallow surface snow to who knows where, rather than steadily building new wind slab layers. However, keep an eye out for isolated pockets of wind slab that may have formed on a variety of terrain features.  The Pro Patrol at Mt Hood have indicated that the recent new snow is no longer in sight, given the recent strong winds.

The mid and lower snowpack at Mt Hood snow consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

Detailed Forecast for Monday:

Clearing skies, cool temperatures and increasing northerly crest level winds are expected Monday. Watch for new shallow wind transport to more southerly facing slopes, especially near and above treeline where stronger winds are expected. 

Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow (new or existing) to pose an avalanche hazard.