Snoqualmie Pass

Issued: 6:00 PM PST Sunday, March 18, 2018
by Josh Hirshberg

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.

While avalanche conditions are slowly easing, Low Danger does not mean no danger. Deep Persistent Slab avalanches are very difficult to trigger, but the potential for high consequences lurks deep in the snowpack. Weak layers buried deep in old snow have been responsible for fatalities and serious injuries each of the past four weekends.

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Avalanche Problems for Monday

Persistent Deep Slabi

Deep, persistent slabs are destructive and deadly events that can take months to stabilize. You can triggered them from well down in the avalanche path, and after dozens of tracks have crossed the slope. Give yourself a wide safety buffer to handle the uncertainty, potentially for the remainder of the season.

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Forecast for Monday:

While Deep Persistent Slabs are very difficult to trigger, the resulting avalanche could be so large and destructive that you will have little chance of surviving. Persistent weak layers have been the cause of avalanche fatalities or serious injuries every weekend for the past 4 weeks. Recent test results and avalanches show that these layers can still be triggered. Currently, you will see significant backcountry traffic in avalanche terrain, but little signs of avalanches. The best way to stay safe from the potential consequences is to limit your exposure to large avalanche paths. Stay out of start zones and large, complex avalanche paths.

Until southerly slopes get softened by the sun they will remain hard and slick. If you travel on these slopes while they are still firm it may be difficult to stop a fall. Avoid traveling near or under areas with glide cracks and stay out from under large cornices. 

Avalanche Summary:

Expect cool temperatures and a mix of sun and clouds for Monday. If the sun comes out, it could soften the surface of sun-exposed slopes. While there may be a few rollerballs in areas that received a couple inches or more of recent snow, Loose Wet avalanches should not be a problem. A dusting of light snow on Saturday and Sunday followed a warm, sunny stretch at the end of the work-week. Many sunny slopes have very hard crusts in the top foot of the snowpack. High elevation, northerly slopes are staying soft and dry.

Below this most recent crust a variety of snowpack structures have been reported. Most observations indicate strong layers of dry snow intermixed with various melt freeze crusts. In isolated locations, thin buried persistent weak layers have been reported. You are most likely to find a buried persistent weak layer in shaded locations, at higher elevations, and/or in terrain slightly east of the Cascade Crest.

A more widespread persistent layer continues to be found 3-6 feet below the snow surface. A thin layer of weak sugary facets have been observed just above a stout crust (2/8). While some Compression Test and Extended Column Tests may show results on this deep weak layer, many will not. Deep Tap tests and Propagation Saw tests will yield the most reliable results. While snowpack tests may demonstrate the presence of a weak layer, they are difficult to interpret and are not a good tool for determining whether or not a slope is safe.



NWAC forecaster Dallas Glass was in the Stevens backcountry Wednesday. Dallas observed 6 inches of new snow bonding well to a semi-supportable and strengthening crust. He observed the 2/8 layer down 4 feet in most locations.


NWAC professional observer Jeremy Allyn traveled in the Alpental Valley Saturday. Jeremy found unsupportive snow on steep sunny slopes by afternoon. He observed many loose wet avalanches up to D2 from the past few days, as well as glide cracks opening on low elevations rocky slopes.  

On Saturday, observers reported a large wet natural avalanche that stepped into older layers on a SW aspect at 4500ft near Red Mountain.


NWAC Forecaster Dallas Glass was in the Paradise area of Mt Rainier on Saturday. Dallas found a very hard, frozen crust about 1 foot thick on sunny slopes. He also reported sudden test on the 2/13 facets about 4 feet below the surface.

NWAC professional observer Jeremy Allyn traveled in the Crystal backcountry Thursday. Jeremy found 6 inches of new dry snow moderately bonded to a newly forming crust. He observed limited new loose surface snow concerns on steep sunny slopes. The 2/8 layer was found down 4 feet.

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.