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Avalanche Forecast

Archived

Jan 12th, 2018–Jan 13th, 2018

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

Regions

Mt Hood.

Icy conditions near and below treeline will limit avalanche danger and make travel difficult Saturday. Above treeline a high level of uncertainty exist due to several days of significant precipitation, wind, and limited visibility. Venture cautiously into above treeline terrain until more information can be gathered.

Detailed Forecast

Precipitation should taper off quickly Saturday morning with clearing skies and improving visibility expected by late morning. Warm air temperatures and increasing sun will have a difficult time effecting the rain/freezing rain crust formed Friday.

Icy surface conditions below and near tree line will great reduce the avalanche hazard at these elevations. Uncertainty exists around the upper elevations regarding the recent rain/freezing rain event.

Recent weather has limited our observations above treeline. Firm wind slabs likely exist on lee and cross-loaded slopes. Give these areas respect as they may be difficult to trigger but could produce very large avalanches.

Expect difficult travel conditions this weekend with icy conditions at lower elevations and varied snow surfaces at higher elevations.

Snowpack Discussion

A strong weather system initially brought snow to Mt. Hood on Thursday followed by rain and freezing rain through Friday morning. This has created a strong surface ice crust up to at least 7300 feet. Above treeline, strong winds and very limited visibility has made travel extremely difficult and observations nearly impossible. W-SW winds Wednesday through Friday combined with significant snowfall at higher elevations has likely created a variety of snow surfaces including firm wind slabs in the alpine. 

Observations

On Friday, observations were limited due to low visibility, but a thick ice crust was observed from 5900 ft to 7300 ft in the Mt. Hood Meadows area. The ice crust was preventing wind transport of recent snow. 

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.