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Avalanche Forecast

Archived

Jan 11th, 2018–Jan 12th, 2018

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

Regions

Mt Hood.

Dangerous avalanche conditions will persist on Friday, especially near and above treeline. Recent and fresh deep wind slab will exist near and above treeline. Time and patience is required to let recent storm snow instabilities heal. Small loose wet avalanches could become consequential around terrain traps below treeline. Travel conservatively Friday.

Detailed Forecast

Snow levels should eventually settle around 4500 feet  on Friday. Light to moderate showers seen through Friday morning should taper down in the afternoon. 

Dangerous avalanche conditions will persist on Friday, especially near and above treeline. Recent and fresh deep wind slab will exist near and above treeline. If visibility allows, look for evidence of recent large or very large natural wind slab avalanches that may have released in the alpine and run long vertical distances. 

Time and patience is required to let recent storm snow instabilities heal. Small loose wet avalanches could become consequential around terrain traps below treeline. Travel conservatively Friday.

Snowpack Discussion

A strong storm system Wednesday night and Thursday brought strong winds and heavy precipitation to Mt. Hood. Several inches of heavy wet snow accumulated near and above 6000 feet on Mt. Hood Thursday, with storm totals increasing further through the afternoon and evening hours as the snow level dipped below 5500 feet late Thursday afternoon.  W-SW winds were strong near and above treeline, making observations nearly impossible.

Observations

No avalanche activity was noted by mid-day Thursday in the Mt. Hood Meadows area at 5500 feet or below. 

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.