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Avalanche Forecast

Archived

Feb 25th, 2015–Feb 26th, 2015

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

Shallow storm and wind slabs are possible Thursday primarily on lee slopes above treeline. 

Detailed Forecast

A few inches of new snow may accumulate above 4500-5000 feet Wednesday night through Thursday afternoon on Mt. Hood. The new snow along with a slight warming trend Thursday afternoon may make for locally unstable and shallow storm and wind slabs, especially on lee slopes above treeline.  

Watch for new snow bonding poorly to the old snow surface; likely a variety of surface crusts and older wind transported snow. 

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. 

Snowpack Discussion

Since the wet start to February, fair weather through mid-February has led to generally thick surface crusts, as well as further deterioration of the snow cover below treeline.

Weak weather disturbances passed through in NW flow aloft Thursday and Friday, bringing an inch or two of new snow near and above treeline for Mt. Hood. Mt. Hood Meadows pro-patrol reported Sunday morning that although E-NE winds were strong, there was minimal snow available to build new wind slab. 

Generally low avalanche danger along with fair and mild weather has been observed mid-week. 

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.

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.