West Slopes Central - Skagit River to South of I-90

Issued: 8:31 PM PST Thursday, January 18, 2018
by Kenny Kramer

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. 

Human-triggered avalanches are likely on Friday. New snow and moderate SW winds will combine to create sensitive wind slabs near and above treeline. The danger increase will be storm snow dependent. Both storm and wind slab will increase in size throughout the day. 

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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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Storm Slabsi

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.

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Avalanche Summary:

New storm snow amounts varied according to elevations as rain gradually changed to snow Wednesday night. As of Thursday evening, storm snow since Wednesday below 4000' is about 4-6 ", near 4000' about 8-10' and above 5000' about 12-16".

Above treeline, greater new snow amounts and periods of very strong winds have caused dangerous avalanche conditions. New wind and storm slabs in higher exposed terrain will require careful terrain choices and conservative decision making.  

Near and below treeline the precipitation began as rain and transitioned to snow. This has caused less dangerous conditions with new snow forming good bonding to the old rain soaked snowpack. However, heavy snowfall and moderate to strong winds have built increasing wind and storm slabs at progressively lower elevations. There are still dangerous avalanche conditions with new and increasingly deep wind and storm slabs of 1 ft or more as of late Thursday.

The old rain wet snow continues to gradually re-freeze and form a new crust layer.

The older snowpack has undergone several rain or warm periods and remains void of any significant layers of concern.



Thursday morning, the Mt Baker Pro Patrol reported fresh wind slabs were sensitive to ski cuts and were releasing in the 4-5 inch range, near treeline. Winds were reportedly very strong along ridges and actively transporting the new snow. 

On Wednesday afternoon, Mt. Baker Pro Patrol observed evidence of several large, natural loose wet avalanches visible on Shuksan arm at approximately 3000 ft. The avalanches are suspected to be from earlier Wednesday. 


NWAC forecaster, Dallas Glass was on Skyline Ridge at Stevens Pass Thursday and reported new storm snow of 8 inches at 4000 feet and 14 inches above 5000 feet. The bonding was good to the old rain wet snow. The crust had yet to re-freeze but was in the process. There was evidence of recent wind transport with a fresh natural avalanche having released on a steep east face about 5300 feet, likely during a brief warm up Wednesday night. There were storm slab layers noted from fluctuating temperatures overnight, but were not sensitive to human trigger in that location. 


Pro Patrol at Crystal Mountain Thursday morning reported shallow 2-4" very soft slabs were sensitive to ski triggers on control. These slabs were breaking up and running as very soft slabs and were generally shallow. The underlying rain crust have become very firm by Thursday morning above 6000 ft and gradually softer at lower elevations.

Forecast for Friday:

Cool temperatures, moderate snow showers and periods of moderate S-SW winds will continue to deposit new snow and further build existing wind and storm slab layers.

Note that a refreezing 1/17 rain crust will continue to harden and may provide a bed surface for wind and storm slab avalanches on Friday.

Building wind and storm slabs should maintain dangerous avalanche conditions near and above treeline. Storm slabs may form quickly and become sensitive to human triggering, especially in those areas receiving the greatest amounts of new snow (more than about 8" of new snow accumulated) and higher snowfall rates (extended periods of more than about 2" per hour). 

Conservative terrain choices will be essential in higher and wind exposed terrain. Best to travel in wind sheltered, lower elevation terrain well away from steep open slopes until this new storm snow stabilizes. 


No Corresponding Mountain Weather Forecast Available


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.