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Mt Hood

Issued: 6:00 PM PST Friday, April 20, 2018
by Dallas Glass

See the NWAC Spring Schedule 2018  for details on avalanche forecast products for the remainder of the season.

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.

New and shallow wind slabs may form on lee slopes near and above treeline Saturday. If you see fresh cornices, drifted snow, or uneven snow surfaces, fresh wind slabs may have formed on nearby slopes. Older deeper wind slabs may still be found in isolated areas on steep northerly aspects at higher elevations. Watch for small loose wet avalanches on steep sunny slopes in the afternoon. 

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Avalanche Problems for Saturday

Wind Slabi

Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.

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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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Forecast for Saturday:

A frontal system passing through the Mt. Hood area early Saturday morning should bring much cooler temperatures, a fresh round of wind but only light amounts of new snow above 4000-5000 feet. More sun than cloud is expected in the afternoon as showers decrease. Snow levels will remain cool for April on Saturday. 

New and shallow wind slabs may form on lee slopes near and above treeline Saturday. If you see fresh cornices, drifted snow, or uneven snow surfaces, fresh wind slabs may have formed on nearby slopes. Wind slabs that formed on many slopes near and above treeline earlier in the week should be trending from stubborn to unreactive. Older deeper wind slabs may still be found in isolated areas on steep northerly aspects at higher elevations.  

Mid-day and afternoon sun breaks may allow small loose wet avalanches to release on steep sunny slopes. Look for signs of wet surface snow developing as you travel. New rollerballs, fresh fan shaped avalanche debris, and wet surface snow deeper than your ankle all indicate the potential for loose wet avalanches has developed on similar steep slopes. Avoid slopes with terrain traps where even a small loose wet avalanche could have unintended consequences. 

Cornices over the winter have grown very large. Do not linger below slopes overhung by large cornices or where a cornice fall may trigger larger deeper avalanches.

Avalanche Summary:

Warm and generally sunny weather affected the snow in the Mt Hood area Thursday and Friday. On slopes receiving sunshine and on lower elevation slopes, moist surface snow conditions developed. Cold drier surface snow may still be found on shaded slopes at higher elevations. The mild weather has allowed many of the recently formed wind slabs time to gain strength.

Significant snowfall accumulated in the Mt Hood area earlier in the week. Around 16-20 inches (40-50 cm) of snow fell Sunday (4/15) through Tuesday (4/17). Strong west-southwest winds during the storm transported the new snow forming wind slabs on many slopes at higher elevations.

While numerous layers can be found within the snowpack, there are no significant layers of concern at this time.

Observations

On Thurday, NWAC professional observer Laura Green traveled in the Mt Hood backcountry. Laura found wind slabs on NE-E aspects near treeline. These wind slabs were still reactive in some snowpack tests. On south-facing slopes, she observed large rollerballs up to 3 ft (90cm) in diameter.

On Wednesday, NWAC received reports through Mt Hood Meadows ski patrol of a skier triggered wind slab avalanche outside the ski area. The avalanche was triggered by a backcountry user and estimated to be about 2 feet deep.

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.