Avalanche Forecast
Regions: Mt Hood.
Wet snow conditions will persist, maintaining the potential for glide avalanches on steep unsupported terrain features that may not have released during recent heavy rains. Much of the below treeline elevation band does not have enough snow cover to support an avalanche hazard. Watch for non-avalanche related hazards such as open creeks and barely buried rocks and trees.
Detailed Forecast
Periods of light rain are expected Saturday night through Sunday morning for Mt. Hood. By late morning precipitation should increase as the cold front should pushes through in the afternoon dropping snow levels to 4000-4500 feet by 4 pm. Â
Wet snow conditions will persist, maintaining the potential for glide avalanches on steep unsupported terrain features that may not have released during recent heavy rains. Much of the below treeline elevation band does not have enough snow cover to support an avalanche hazard.
Watch for the numerous travel hazards such as open creeks, barely buried rocks and trees, and glide cracks, creating poor and challenging travel conditions, especially below treeline.Â
Remember that closed ski areas without avalanche mitigation are equivalent to backcountry terrain! Â
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Snowpack Discussion
New resources within your Avalanche Forecast this season!Â
The Mountain Weather tab will take you to the most recently issued Mountain Weather Forecast. The Observations & Weather Data tab will allow an easy view of the various weather station graphs within your zone of interest and provide easy access to the most recent avalanche and snowpack observations.Â
The great start of winter 2017/18 in the PNW has taken a recent hit as warm wet weather arrived early Monday morning in the Mt Hood area and has just begun to cool as of late Thanksgiving. The Mt Hood weather stations received over 5 inches of rain since Monday morning, reaching well above the Cascade crest level.
No recent avalanche observations have been received from the Mt Hood area, however the warming and rain initially triggered numerous wet snow and glide avalanches earlier this week in the WA Cascades, mostly reported on Tuesday and Wednesday, especially on steep unsupported slopes and rock faces where many glide avalanches released.Â
Rain has now melted significant snow with average snow depths decreasing about 50-60% since Monday! This has allowed much of the previously well snow covered terrain to open with many creeks and snow bridges re-appearing, especially near and below treeline.Â
Cooling since Thursday with additional, mostly light precipitation, has begun to add some new snow above the old wet snowpack. Very shallow new snow has accumulated since Friday.
Observations
No direct snowpack or avalanche observations have been received in the Mt Hood area, however, similar conditions to the WA Cascades are expected and some recent observations from Washington are offered below.
A few NWAC observers began assessing the post deluge Friday, Nov 24, both in the Mt Baker and Alpental Valley backcountry.Â
In the Baker region, the key takeaway is just how much the snow cover has diminished with travel becoming significantly more challenging and hazardous due to open creeks and shallow snow. Most of the observed recent wet snow or glide avalanches were estimated to be two or more days old. The most recent storm snow, up to about 6 inches, was reluctant to release on steep test slopes with storm layers appearing to rapidly settle with near freezing temperatures. No direct observations were made above treeline.
In the Alpental Valley, a similar story is told with evidence of numerous glide avalanche releases from steep unsupported terrain and rock faces. Travel conditions, especially below treeline, are now difficult with numerous early season challenges and hazards having quickly returned.   Â
Avalanche Problems
Glide Cracks
A release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often preceded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
Predicting the release of Glide avalanches is very challenging. Because Glide avalanches only occur on very specific slopes, safe travel relies on identifying and avoiding those slopes. Glide cracks are a significant indicator, as are recent Glide avalanches.
This Glide avalanche broke to the ground on a smooth, grassy slope. From all the mud on the bed surface, water pooling at the base of the snowpack likely caused the failure.
Glide avalanches occur when water lubricates the interface between the snowpack and the ground. These avalanches are difficult to predict and best managed by avoiding terrain below glide cracks.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Unlikely
Expected Size: 1 - 1