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East Slopes Central - Lake Chelan to South of I-90

Issued: 6:04 PM PST Thursday, February 1, 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. 

Precipitation type and amount will increase the avalanche hazard in most areas Friday. In areas with snow, identify and avoid areas where strong winds are depositing snow such as below cornices, on wind dirfts, and on cross-loaded features. In locations receiving rain, wet avalanche conditions will develop. Avoid terrain where being caught in a small avalanche could have higher consequences such as above cliffs, creeks, or gullies.

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Avalanche Problems for Friday

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 Friday:

Warm wet weather and strong winds will increase the avalanche danger along the east slopes of the Cascades Friday. Avalanche conditions will be dependent of precipitation type and amounts.

In locations receiving snow, winds will continue to build Wind Slabs that can be triggered by a person. Identify and avoid avalanche terrain where winds are depositing snow. Fresh cornices, wind drifts, plumes of snow, and uneven snow surfaces all indicate that Wind Slabs are present. Winds Slabs can be difficult to assess. Use wide margins of safety when traveling in and around wind deposited snow.

In locations receiving rain, wet avalanche conditions will develop. You will be able to trigger Loose Wet avalanches on steeper slopes. Watch for roller balls and pinwheels as these area a sign that Loose Wet avalanches are becoming more likely to trigger.

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.

Avalanche Summary:

As of Thursday afternoon soft surface snow was found in most locations along the east slopes of the Cascades. Light snow showers, cool air temperatures, and generally light winds have allowed surface snow to settle and gain strength. The snowpack has not received a significant loading event since Monday.

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. The Northeast Cascades, including WA Pass, received all snow throughout Monday’s storm.

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

NWAC pro-observer Jeff Ward was in the Hairpin area of Washington Pass on Wednesday.  He found generally right-side-up snow conditions. No new avalanche activity was observed since the Jan 29th cycle. 

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. They found the 1/16 crust down 5 feet in most areas.

Central

A professional in the Holden area Tuesday observed evidence of a widespread loose wet cycle from 1/29 primarily in start zones below 6000'. The largest slides were up to size D2.5. It is estimated that rain reached up to 6000 feet in this area.  There was 6" on top of the 1/30 crust.

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

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.