West Slopes North - Canadian Border to Skagit River

Issued: 9:08 PM PST Saturday, March 3, 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.

An avalanche in the North Fork of the Teanaway resulted in 2 fatalities on Saturday. An NWAC forecaster visited the location of the avalanche and more details will be made available as soon as we have them.

Despite the continued slow stabilizing trend, specific terrain still has the potential to produce large and destructive avalanches. You may trigger a Wind Slab avalanche near and above treeline or a persistent slab avalanche on the southern half of the compass. Persistent slabs surprise travelers by breaking widely across a slope. Avoid large open slopes on solar aspects greater than 35 degrees and recently wind loaded areas in higher terrain.  

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Avalanche Problems for Sunday

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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Persistent Slabi

Persistent slabs can be triggered by light loads and weeks after the last storm. You can trigger them remotely and they often propagate across and beyond terrain features that would otherwise confine wind and storm slabs. Give yourself a wide safety buffer to handle the uncertainty.

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Forecast for Sunday:

Minimal weather inputs are expected on Sunday as clouds increase, but light snow showers shouldn't become widespread until late in the day.

You are most likely to trigger Wind Slab avalanches above treeline. You can avoid these avalanches by staying off of recent snow drifts, deeply pillowed features, and fresh cornices on slopes 35 degrees and steeper. These areas may exist far below ridge-lines and on mid-slope cross-loaded features. Soft non-wind-effected snow may cover new wind slabs making them harder to identify. 

You may be able to trigger Persistent Slab avalanches in the upper snowpack on sun-exposed slopes (generally southerly aspects) greater than 35 degrees. In specific terrain, if you dig about 2-3 feet below the surface you will find a series of thin sun crusts surrounded by very small facets. If you find this layer, avoid steep, open, sunny slopes as well as large avalanche paths to reduce your risk of these difficult to manage avalanches.

Loose Wet avalanches are unlikely on Sunday because clouds should be arriving during the morning hours.

Avalanche Summary:

On Saturday morning, sunshine impacted the surface snow on solar aspects creating numerous small Loose Wet avalanches. Snowmachines were able to trigger large wind slabs formed earlier in the week on the south side of Mt. Baker Saturday. 

The last major storm cycle wrapped up Wednesday morning and during this period, new snow combined with periods of moderate to strong winds transported snow in exposed terrain forming wind slabs. About seven inches of snow has accumulated in the last two days and four feet of new snow has fallen in the last week at Mt. Baker ski area.

On E-S-W aspects, a thin breakable sun crust was formed early last week and buried on 2/23. Very small weak facets have been reported surrounding the crust. This layer has not yet had significant time to heal. It is found approximately 3 feet below the surface on steeper slopes that have received direct sun during the past week.

Some observations suggest the presence of other persistent grains at this same interface on shaded slopes. Buried surface hoar and large preserved stellars have been reported in recent avalanches and snowpack tests at this interface in other parts of the Cascades.

Observers continue to report potential for a Deep Persistent Slab avalanche on a layer of weak sugary facets buried on 2/13. This weak layer is generally 3 to 5 feet below the snow surface just above a very firm melt-freeze crust (2/8). It's worth paying attention to this layer if your venturing into shallower snowpack areas. While these avalanches are unlikely, the consequences could be grave.

There are no significant layers of concern below the 2/8 crust.


On Saturday, an NWAC professional observed two large wind slab avalanches several feet deep triggered by riders on the Easton Glacier around 6000'.

On Saturday, an avalanche professional in the Bagley Lakes area noted recent wind transported snow in the near treeline zone, but no skier triggered avalanches on that wind-affected snow. Small loose avalanches were triggered by sunshine and the sun influenced the release of slab avalanches that approached large (D2) in specific terrain features on the south side of Mt. Herman. On east aspects, the 2/8 crust was down 60 inches or more and facet crystals above this layer were rounding. No other significant layers were present on this aspect.

On Wednesday NWAC professional observer Lee Lazzara traveled in the Mt Baker backcountry. Lee reported wind slabs forming on a variety of aspects near treeline. Snowpack observations showed a highly variable snowpack, but the facet/crust combination was found on steep sunny aspects 2 feet below the snow surface.

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.