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Avalanche Forecast

Archived

Feb 5th, 2015–Feb 6th, 2015

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

Regions

Mt Hood.

The avalanche danger Friday will center around wet avalanche concerns and become increasingly dangerous with elevation.

Detailed Forecast

Moist and mild southwesterly flow will carry wet fronts across the area Thursday night and Friday. Snow levels will remain high, around 8000 feet, before beginning to cool later Friday afternoon. Mt. Hood will receive less precipitation than the Washington Cascades Thursday night and Friday.  

The avalanche danger Friday will center around wet avalanche concerns and increase with elevation. Small loose wet avalanches are possible below and near treeline, with the potential for larger wet loose and wet slab avalanches above treeline where more recent snow is available for entrainment above the most recent rain crust on lee aspects.

Remember, due to the unseasonably low snowpack especially at lower elevations, numerous terrain hazards such as open creeks, partially covered rocks and vegetation are widespread.  

Snowpack Discussion

Mild weather with sunny days or minor rain or snow was seen from about January 26th to about January 31st. This caused more consolidation, stabilizing and the formation of a thick strong stable surface crust in most areas west of the crest including Mt Hood.

Slightly wet weather from about February 1st through 4th produced about 5 inches of snow at NWAC sites at Mt Hood mixed with periods of rain. A frontal system Thursday pushed snow levels up to around 8000 feet in the afternoon with light rainfall accumulations at NWAC sites. 

Mid-week the Meadows patrol reported sensitive ski triggered 2-6 inch storm slab avalanches. On Wednesday, NWAC observer CJ Svela reported some natural loose wet avalanches and cornice drops on east aspects in the White River Canyon above treeline.

The mid and lower snowpack at Mt Hood should consist 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.

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.