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Olympics

Issued: 8:43 AM PST Wednesday, February 7, 2018
by Robert Hahn

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. 

Updated 8:40 AM: Warmer than forecast temperatures Wednesday resulted in an update include loose wet avalanches in all elevation bands on the west slopes of the Cascades and to add the problem near and below treeline on the east slopes. Lower-than-forecast wind speeds have resulted in a reduced wind slab hazard in both the Cascade West-North zone and Cascade East-North zone above treeline. The potential for wind slab development has been reduced and the anticipated hazard has been reduced accordingly from considerable to moderate.

Rapidly warming temperatures will increase the danger of loose wet, cornice and glide avalanche problems, particularly during the afternoon hours. Loose wet avalanches are possible to trigger on steep slopes with wet surface snow. Avoid travel beneath corniced slopes, under rock faces where glide cracks may exist, or where avalanches may carry you into terrain traps.

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Avalanche Problems for Wednesday

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 Wednesday:

The Hurricane Ridge area will see very significant warming, with snow levels rising to the top of the above treeline terrain on Wednesday. Mostly cloudy skies are expected with a slight chance of a light rain shower.

Small to large loose wet avalanches are possible on all aspects and at all elevations on Tuesday as significant warming combine with the potential for sun breaks or light rain showers warm the snow. You are more likely to trigger a loose wet avalanche at lower elevations where wet snow conditions extend deeper in the snowpack. Loose wet avalanches may be small to large in size and may run farther and entrain more snow than you expect on Wednesday.

Large cornices exists primarily on NW-SE aspects along ridgelines in the Hurricane Ridge area. Recent mild air temperatures and rain have made these massive blocks of snow more likely to fail. After a several days of cooler weather, additional warming on Wednesday will increase the likelihood of failure, so continue to give cornices a wide berth and avoid travel directly below corniced slopes. 

Several glide cracks have been reported recently by NPS rangers. Glide avalanches occur in locations where wet smooth ground surfaces allow the entire snowpack to avalanche. Glide avalanches are highly unpredictable and as their releases generally are not tied to peak warming or rainfall. If you see glide cracks on a slope, avoid traveling on or below that terrain. While you are unlikely to trigger a glide avalanche, a glide avalanche would be large and deadly. With limited rain at Hurricane Ridge, the probability on Tuesday is quite low, but continue to travel around open cracks and rock faces with caution.

Avalanche Summary:

Fair weather has returned to hurricane ridge, with cooling to slightly below freezing with diurnal warming to slightly above freezing. A melt-freeze cycle is likely to be seen with the surface snow conditions and some initial warming trend is starting to be seen during the day on Tuesday as a high pressure brings warmer air to the Olympics before the Cascades.

Light rain was seen Saturday afternoon through Sunday morning along with mild temperatures caused wet surface snow conditions over the weekend. Significant snowpack settlement continues to occur in the Hurricane Ridge area with the recent warm and wet weather. On Friday, several natural wet loose avalanches were observed at all elevations.

Large cornices developed during the last two weeks of January along ridgelines near and above treeline.

The recent warm and wet weather has produced glide cracks on slopes with smooth ground surfaces. Observations indicate glide cracks in common locations such as 20th of June, Steeple, and the Steep-and-Icy avalanche paths.

Observations

NWAC pro-observer Matt Schonwald and NPS Rangers traveled in the Mt Angeles areas Friday. They observed moist to wet surface snow up to 6000 feet. Wet loose avalanches were seen releasing during sunny breaks around mid-day. They identified and avoided traveling near or below large cornices.

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.