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Avalanche Forecast

Archived

Dec 22nd, 2017–Dec 23rd, 2017

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

Fresh storm and winds slabs will continue to form in the Mt Hood area from yet another round of precipitation Friday afternoon into Saturday morning. Saturday is a time for cautious terrain travel especially above treeline.

Detailed Forecast

New snow falling Friday night into Saturday morning will continue to develop new storm and wind slabs around the Mount Hood backcountry. Watch for wind loaded snow near ridge crest and mid-slope cross-loaded terrain features. Winds will vary with height on Mt. Hood Saturday; expect easterly winds around 5000 feet and W-NW winds in the above treeline and higher elevation bands. 

Shallow storms slabs will form in wind protected areas. Even small avalanches triggered within the new storm snow may entrain soft snow from earlier in the week causing them to grow larger than anticipated.

Early season snow conditions still exist. Be particularly cautious of creeks as many of them have not become snow covered for the winter.

Snowpack Discussion

Several inches of new snow have accumulated in the Mt Hood area by Friday afternoon with more expected Friday night. Moderate to strong winds accompanying this band of moisture will likely have formed fresh wind slabs on lee slopes near and above treeline.

Around a foot of recent snow now sits atop Monday’s freezing rain layer. However due to significant wind transportation of snow especially near and above treeline, height of snow can vary dramatically across terrain.

No recent activity avalanche has been reported in the area.

Observations

Backcountry observations from Thursday confirm the wind redistribution of snow, with bare ridges and wind slabs on lee slopes observed.

Mt Hood Meadows pro patrol reported wind slabs near and above treeline formed earlier in the week. Control efforts on wind slabs within the ski area produced limited results.

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.