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Avalanche Forecast

Archived

Feb 2nd, 2016–Feb 3rd, 2016

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

Regions

Mt Hood.

Expect increasing avalanche danger Wednesday afternoon with new storm and wind slabs developing. Travel conservatively, especially avoiding wind loaded slopes above treeline Wednesday. 

Detailed Forecast

New storm and wind slab should build Wednesday afternoon as a Pacific frontal system approaches from the west. 

Storm slabs should be shallow but should become increasingly sensitive due to a slight warming trend during the day. S-SW transport winds will build wind slab on lee aspects. Watch for signs of cracking or firmer wind transported snow. Older and larger wind slabs may still be sensitive on similar aspects above treeline. 

New snow may initially bond poorly to a variety of snow surfaces Wednesday. Travel conservatively and expect a rising avalanche hazard later in the day. 

 

 

Snowpack Discussion

Weather and Snowpack

A strong front crossed the Northwest on Friday January 29th. NWAC stations at Mt Hood had about a foot of new snow by Saturday morning. About another 6-8 inches followed at the tail by Sunday morning. Cool and benign weather settled over Mt. Hood the last few days with ample sunshine on Tuesday.

Recent Observations

On Sunday the Mt Hood Meadows patrol reported limited 4-6 inch wind slab on lee slopes in the above tree line, lower than usual below ridges, which would be small and difficult for a skier to trigger.

A report on Turns All Year for Sunday in Newton Canyon had gradually harder compression tests with depth in right side up storm snow with no signs of propagation.

The Mount Hood Meadows pro-patrol on Monday reported minor wind transport in the above treeline giving isolated, small pockets of wind slab. Also on Monday, NWAC pro-observer Matt Schonwald found wind slab around 7000' on a ESE aspect in White River Canyon failing during snowpit tests at a density change 30-60 cm down. The slab was pencil hardness.  Matt found the wind slab hardness and sensitivity quickly decreased with a loss in elevation. 

On Tuesday, the Meadows pro-patrol ventured well into their above tree-line terrain (Super Bowl). They found wind slab on lee aspects failing at a density change 40-45 cm down but not particularly reactive in snowpack tests.

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.