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Avalanche Forecast

Archived

Feb 6th, 2015–Feb 7th, 2015

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

Regions

Mt Hood.

Expect increasing avalanche danger with elevation on Saturday... with new storm and wind slab avalanches possible near and above treeline. 

Detailed Forecast

Lowering snow levels and light to moderate precipitation late Friday night and Saturday should build new storm and wind slab above about 6000 feet. The avalanche danger should increase with elevation Saturday. 

The below treeline snowpack should be well drained and capable of handling additional rain without a significant increase in avalanche danger. Small wet loose avalanches will still be possible on steeper slopes below treeline. 

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. Frontal systems Thursday and Friday pushed snow levels up to around 7000-8000 feet 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.

On Friday, the Meadows pro-patrol reported that the most recent snow was wet but well bonded and not causing any significant loose wet problems near and below 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

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

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.