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Avalanche Forecast

Archived

Feb 12th, 2019–Feb 13th, 2019

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

Deep new snow combined with very strong winds and warming has created dangerous avalanche conditions requiring conservative terrain choices Wednesday. Avoid steep slopes greater than 35 degrees, especially higher terrain that received wind deposited snow where you are likely to trigger life-threatening avalanches. Avalanches could be large and run far and fast.

Discussion

Snow and Avalanche Discussion

Since Sunday morning an impressive 3 ft or more of new snow has fallen in the Mt Hood area! The early storm snow fell with cold temperatures and more recent snow with gradual warming and very strong winds Monday night and Tuesday. All this storm snow is sitting on a hard crust and in areas is poorly bonded due to weak faceted crystals that formed on the crust. Widespread natural and controlled avalanches were reported Tuesday at Mt Hood Meadows. There were both soft and hard slab releases with many slides releasing to the crust layer, buried 3-6 ft or more in wind loaded terrain. Storm slabs were also sensitive to human trigger to lower elevations Tuesday, with some slides running fast and far. It will take extra time for these dangerous conditions to stabilize requiring conservative terrain choices. The safest and best conditions exist on lower angled terrain in wind sheltered locations.

Snowpack Discussion

New Regional Synopsis Coming Soon

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.