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Mt Hood

Issued: 8:52 AM PST Friday, December 29, 2017
by Garth Ferber

NWAC avalanche forecasts apply to backcountry avalanche terrain in the Olympics, Washington Cascades and Mt Hood area. These forecasts do not apply to developed ski areas, avalanche terrain affecting highways and higher terrain on the volcanic peaks above the Cascade crest level.

850 am Friday December 29: Hurricane and East Slopes of the Washington Cascades forecasts adjusted.

There should be enough heavy rain on Thursday and Friday to break down the recent freezing rain crusts and tap into softer snow below the crusts and cause loose wet snow avalanches. Wet slab avalanches seem possible.

Avoid the lower parts of avalanche paths that start higher on the mountain!

Danger Scalei
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Avalanche Problems for Friday

Loose Weti

Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

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Wet Slabsi

Wet slabs occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoiding avalanche paths when you see pinwheels, roller balls, loose wet avalanches, and during rain-on-snow events.

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Forecast for Friday:

The active changeable pattern will continue on Friday. Another moist system arrives on a SW flow. A surface low will track across across NW Washington and a cold front will move across the Cascades Friday evening. What this means at Mt Hood is stormy crest level winds and a lot of rain on Thursday night and Friday.

The outcome of so much rain and the current snowpack at Mt Hood is difficult to predict. There should be enough heavy rain on Thursday and Friday to break down the recent freezing rain crusts and tap into softer snow below the crusts and cause loose wet snow avalanches. Wet slab avalanches seem possible.

Here is a big heads up for Mt Hood: avoid the lower parts of avalanche paths that start higher on the mountain! Large or very large avalanches starting from higher on the mountain and running into the above, near and below treeline areas seem possible or likely.

Avalanche Summary:

A very big change is underway compared to the past 5 days of quiet weather. The Northwest will experience a very active changeable weather pattern Thursday and Friday with moist systems crossing the Pacific Northwest.

On Thursday strong westerly flow aloft is carrying a very moist occluded front across the NW. Winds and snow are ramping up on schedule at Mt Hood on Thursday at sunset.

The frontal zone will remain over the South Cascades and Hood zones Thursday night with the strongest crest level winds and heaviest rain or snow possibly in the south Cascades and Mt Hood.

It has been an "interesting" past week for weather at Mt Hood with some mixed precipitation including yet more freezing rain Wednesday. A weather disturbance also moved across the southern WA Cascades and Mt Hood area Christmas Eve into Christmas Day, depositing 6-10 inches of snow before unfortunately ending with freezing rain and forming a surface crust. Prior to this storm, about 15-18 inches of low density snow fell at Mt Hood in the 24 hours ending Saturday morning 12/23.

Observations

NWAC pro-observer Laura Green on Thursday reported that the freezing rain crust remained stout and predominant on the surface of the snowpack up to about 7300 ft.

On Wednesday morning 12/27, Mt. Hood Meadows Patrol reported a rain/freezing rain crust at 5200 ft thickening with elevation up to 6600 ft. Some wind transport of recent snow was occurring above treeline. 

On 12/26 the Mt Hood Meadows Patrol reported that wind slabs were more stubborn to trigger during control work. A 1 cm freezing rain crust had formed near the surface.

No Corresponding Mountain Weather Forecast Available

USE AT YOUR OWN RISK

This Backcountry Avalanche Forecast is provided in conjunction with the US Forest Service, and is intended for personal and recreational purposes only. Safe backcountry travel requires preparation and planning, and this information may be used for planning purposes but does not provide all the information necessary for backcountry travel. Advanced avalanche education is strongly encouraged.

The user acknowledges that it is impossible to accurately predict natural events such as avalanches in every instance, and the accuracy or reliability of the data provided here is not guaranteed in any way. This forecast describes general avalanche conditions and local variations will always occur. This forecast expires 24 hours after the posted time unless noted otherwise.