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East Slopes North - Canadian Border to Lake Chelan

Issued: 6:00 PM PST Friday, February 2, 2018
by Dallas Glass

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. 

Ridge top winds will transport snow forming soft new Wind Slabs on lee slopes. Identify and avoid areas of wind deposited snow near and above treeline. Loose Wet avalanches will be possible in locations receiving rain. Stay off of steep slopes where small Loose Wet avalanches may have large consequences.

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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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Avalanche Summary:

Warming air temperatures and showery weather began to change surface snow conditions on the East Slopes of the Cascades Friday. Water amounts varied by location, but in most locations south of Holden rain has fallen up to 6000 feet.

Above 6000’ winds have formed fresh shallow wind slabs up to 6” thick.

A natural avalanche cycle has been reported in many areas from Monday’s warm wet weather. Rain occurred along the east slopes as far north as Holden, WA.

Scattered observations from the last week of January found buried surface hoar on top of the 1/16 crust. This persistent weak layer was found or thought to be the cause of several avalanches. Extra caution should be taken when traveling in areas further east of the crest where this layer may survive. Snow profiles and snowpack tests are the only means to identify and locate this layer.

Observations

North

A guide from NCH Friday reported new and reactive Wind Slabs developing due to strong ridge-top winds. Slabs were observed to be 4 inches thick. 

Tuesday, reports from NCMG in the Cuttthroat drainage of Washington Pass indicated a natural avalanche cycle from Jan 29th. Many of these avalanches were large (D2-D2.5) and some were triggered by cornices falling onto the slope.

Central

An avalanche professional traveling in Icicle Creek Thursday found 6-8” of settled snow well bonded to the 1/29 crust. Observations demonstrated a strong upper snowpack. No buried surface hoar was found in this location.

On Tuesday, Mission Ridge Pro Patrol identified several layers of concern in this regionally shallower snowpack. These layers should be watched during future loading events. Similar basal weak layers were found in the nearby shallow snowpack of Blewett Pass.

South

No recent observations

Forecast for Saturday:

Mild, showery, windy weather will maintain avalanche conditions into Saturday.

Moderate to strong winds will form fresh Wind Slabs on a variety of aspects. Visual clues will help you identify and avoid slopes where winds are depositing snow. Fresh cornices, snow drifts, plumes, and blowing snow all indicate where Wind Slabs are forming. Assessing Wind Slabs can be very difficult. Give this avalanche problem a wide berth until they have time to heal.

In locations receiving rain, wet surface snow conditions will lead to Loose Wet avalanches. You will be able to trigger Loose Wet avalanches on steeper slopes during and immediately following rain events. Avoid slopes where small avalanches may have large consequences such as above cliffs, rocks, creeks, and gullies.

Cornices have grown very large during recent stormy weather. Be aware of cornices overhead. Predicting when and where cornices will fail is extremely difficult. Use extra caution if traveling in areas where cornices exist on ridgelines above.

Avalanche hazard will be lower in areas receiving less precipitation further east of the crest.

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.