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Olympics

Issued: 7:27 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.

Hurricane forecast adjusted 730 am Friday.

As rainfall increases and moves to higher elevations on Thursday, watch for deepening saturated surface snow and avoid consequential terrain features. 

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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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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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Forecast for Friday:

A second storm (Friday) on the heels of the first (Thursday), will bring significantly more precipitation and further warming than the initial system. A surface low will track across across Cape Flattery and a cold front will move across the Olympics Friday afternoon to evening. This will cause moderate SE winds shifting to SW on Thursday at Hurricane, with further warming and increasing rain at Hurricane.

The extent and size of loose wet snow avalanches at Hurricane will depend a lot on the amount on rain received there on Thursday. At higher elevations which have received more snowfall, the loose wet slides will be larger and more dangerous. Watch for initial pinwheels, surface wet snow deeper than a few inches and initial small natural loose wet avalanches that indicated and increasing loose wet avalanche danger.

A little further wind slab development may seen above treeline on Thursday. Watch for possible slightly building wind slab on a variety of aspects above treeline as winds directions shift during the storm.

Also despite all the new snow, early season hazards still exist at some lower elevation locales and especially around creek beds that are not filled in.

Avalanche Summary:

At Hurricane Ridge, the frontal system arriving Thursday brought light snow  with temperatures just below freezing, with light to occasionally moderate SW winds.

Light snow also accumulated during a series of very weak weather disturbances that traversed the area in about the past week. 

The previous significant storm and snowfall was was 12/19-12/20.

Observations

On Wednesday, a shallow loose dry avalanche on a northwest aspect in the Tunnel Path above the road ran 100 feet and knocked a skier off his feet. A pit nearby showed right-side-up snow.

A second hand report of at least one human triggered loose dry avalanche (sluff) caught a skier(s) on Sunday 12/25. No injuries were reported. 

NWAC pro observer Matt Schonwald was at Hurricane Ridge on Saturday 12/24 and reported evidence of north to east winds but no wind slab or significant layers in the upper snowpack. The snowpack structure was generally right-side with good bonds to the Thanksgiving crust.

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.