Issued: 5:33 AM PST Monday, March 5, 2018
by Dennis D'Amico

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.

A serious involvement occurred near Setting Sun Mountain in the Cascade East-North zone on Sunday.

On Saturday, March 3rd an avalanche occurred in the Long's Pass area,  within the North Fork of the Teanaway River Drainage, resulting in two fatalities and serious and minor injuries to two others . The D2.5 (large to very large) hard slab avalanche released on South and West aspects in complex terrain.  The slab released 3' down on a weak layer believed to be the 2/13 facets. NWAC forecasters visited the location of the avalanche both Saturday and Sunday. We are compiling information for a more detailed report.

Snoquamlie Pass forecast updated to include the Storm Slab avalanche problem for Monday March 5th. 

Despite the continued slow stabilizing trend, specific terrain still has the potential to produce large and destructive avalanches. You can still trigger a stubborn wind Slabs near and above treeline on leeward slopes. These could result in dangerous Persistent Slab avalanches that are difficult to manage and can break widely. Avoid wind loaded areas and large open slopes 35 degrees and steeper. 

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Avalanche Problems for Monday

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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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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Forecast for Monday:

Minimal weather inputs are anticipated for Monday with isolated light snow showers.

You may be able to trigger Wind Slab avalanches at upper elevations where drifted wind features exist. Avoid these avalanches by staying off of recent snow drifts, deeply pillowed features, and fresh cornices on leeward slopes 35 degrees and steeper. Soft non-wind-effected snow may cover wind slabs making them harder to identify. If you trigger an avalanche in the upper snowpack, it could step down and become a dangerously large Persistent Slab avalanche.

You may be able to trigger Persistent Slab avalanches on slopes 35 degrees and steeper. Avoid steep, open slopes and large avalanche paths to reduce your risk of these difficult to manage avalanches. Weak sugar-like facets or buried surface hoar can be found just above a firm crust layer formed in early February on all but south aspects. This layer is down about 2-4 feet. 

Avalanche Summary:

Light snowfall increased Sunday afternoon, bringing 2-3" of new snow with light winds. Up to 2 feet of snow fell near Hurricane Ridge in the past week. Winds as recent as Thursday formed Wind Slabs on a variety of aspects near and above treeline. In sheltered areas generally soft unconsolidated surface snow exists. Large snowdepth differences exist between shallow southerly and deeper northerly aspects. 

Some observations suggest other persistent grains may exist at the interface of this week's snow. Facet crust combinations, buried surface hoar, and large preserved stellars have been reported in recent avalanches and snowpack tests at this interface from the West Slopes of the Cascades.

About 3 ft of of settled snow sits on top of the weak persistent grains (see new observation below) that formed on a strong crust earlier in February. Snowpack tests continue to suggest that this interface can fail and produce avalanches. This layer has not been reported on South aspects in the Hurricane Ridge area.

There are no other significant layers of concern in the mid and lower snowpack.


On Saturday March 3rd, NPS rangers found 2-3mm buried surface hoar from mid February intact on a NNW aspect at 4990’. The surface hoar was about 4" (10 cm) above a crust 32" (80 cm) below the surface. No new or recent avalanche activity was observed on this layer. 

On Friday, March 2nd, NPS rangers reported a large avalanche on a recently wind loaded slope. Elsewhere, profiles showed a faceted weak layer buried in mid- February was found 2-4 feet below the surface and was showing some signs of rounding.


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.