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Avalanche Forecast

Archived

Mar 16th, 2015–Mar 17th, 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.
Below Treeline
Natural avalanches unlikely.

Regions

Mt Hood.

It's nearly spring and the sun's strength and high water content of the new snow will make for a locally dangerous mix on steeper slopes above treeline where even a slow moving and shallow avalanche would be powerful and could force you into unintended terrain traps.

Detailed Forecast

Partly to mostly sunny skies and a modest diurnal bump in afternoon temperatures should activate the loose wet avalanche potential on solar slopes near and above treeline Monday. 

It's nearly spring and the sun's strength and high water content of the new snow will make for a dangerous mix on steeper slopes where even a slow moving and shallow avalanche would be powerful and could force you into unintended terrain traps. Changes in the snow will likely be rapid, so think about the avalanche hazard above and below while planning your route Monday.   

Remember the NWAC forecast applies to elevations up to the Cascade crest (~7000 to 8000 ft). Significant new snowfall was received near and above these elevations over the weekend and likely pose a higher avalanche hazard.  

The weekend rain or light snow accumulations along with ample terrain anchors should greatly limit the avalanche danger below treeline. 

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 to cause an avalanche danger.

Snowpack Discussion

The latest installment of warm and dry weather occurred from early March through midweek leading to more snowpack consolidation and a scarcity of avalanche activity. Reports indicated thickening surface crusts on most slopes and some corn snow development on solar slopes. An inch of new snow accumulated above treeline Thursday with rain below. 

Over the weekend, an atmospheric river brought a one-two punch to the Pacific Northwest. Saturday's event brought over 2 inches of rain with the snow line above 7000 ft at Mt. Hood. On Sunday, a low pressure system brought light amounts of precipitation with a snow line of 6500-7000 ft on Mt. Hood. Additional rain and snow is expected Sunday night. Significant new snowfall likely accumulated on the upper volcano Saturday above NWAC's forecast area. 

The snowpack at low elevations remains meager to non-existent. The mid and lower snowpack at Mt Hood consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

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.