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Avalanche Forecast

Archived

Feb 7th, 2015–Feb 8th, 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 a decreasing avalanche danger Sunday with a break between systems. Watch for areas where more significant new snow has accumulated, mainly above treeline and on the volcanoes where new storm and wind slab are likely. 

Detailed Forecast

A break between systems is expected during the daylight hours Sunday. This should give time for any recent shallow storm slab or wet new snow to settle and possibly refreeze to form new surface crust layers. This should allow for a slightly decreasing danger at higher elevations where more recent snow may have accumulated. Watch for wind transported new snow on some higher elevation lee slopes, mainly N-E facing.

The snowpack below treeline should continue to drain, but small wet loose avalanches will still be possible on steeper slopes below treeline. 

Do note as a result of 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 in late January caused further melt, consolidation and the formation of a thick, strong and stable crust.

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. Saturday's storm caused some accumulation above about 6000-6500 feet with up to about 2-4 inches of wet snow.

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

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.

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.

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.