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

Issued: 7:58 PM PST Monday, February 5, 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. 

Gusty winds have created highly variable and unpredictable wind slabs from the top of the below treeline band upwards. Avoid steep wind loaded slopes on any aspect and don't make assumptions about the location, extent, or reactivity of wind slabs until you perform stability tests. Continue to avoid travel under or near corniced slopes.

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Avalanche Problems for Tuesday

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 Tuesday:

Moderate and steady snow levels and insignificant amounts of new snowfall will decrease the overall avalanche danger Monday along the east slopes of the Cascades.

However, moderate and very gusty winds Sunday night through Monday morning continued to form fresh wind slabs on a variety of aspects and elevations, which in some cases have been identified below treeline. Wind slabs are still only 24-48 hours old by Tuesday and may exhibit variable reactivity so avoid steep wind loaded slopes on any aspect. 

Large cornices exist along ridgelines. Cooling temperatures will make cornice failure less likely, but continue to give cornices a wide berth and avoid travel directly below corniced slopes.

The avalanche hazard will be lower in areas receiving less precipitation further east of the Cascade Crest.

Avalanche Summary:

Gusty winds continued to blow snow around on Monday, continuing to creating wind slabs on all aspects and into the below treeline zone in some locations.

Moderate to strong westerly winds at crest level built new wind slabs in the near and above treeline terrain in the northeast Cascades over the weekend. Precipitation was heaviest near the Cascade crest with precipitation rates quickly decreasing further to the east. Little snow was available to transport in areas further south of Holden. Over the weekend and peaking on Sunday, the snow level rose to 5800-6800 feet in the northeast Cascades, and was likely slightly higher further south and east. Wet snow conditions were noted near and below treeline along the Hwy 20 corridor with a wet loose cycle noted below 5500-6000 feet Sunday. 

A natural avalanche cycle has been reported in many areas from Monday’s (1/29) warm and wet weather. Rain occurred along the east slopes as far north as Holden, WA.

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

On Monday, snow professionals in the Washington Pass area reported a recent maximum rain/snow line of 6,800 ft. Subsequent snowfall prevented much refreezing of the wet snow. Winds were unusually gusty and variable with no dominant wind direction and some wind slab was present into the below treeline zone. The party triggered a small wind slab quite low in the terrain. They messaged a high level of uncertainty regarding reactivity and location of wind slabs in this zone. Glide activity was also evident to 6000'.

On Sunday, snow professionals at the Barron Yurt near Hart's Pass reported stormy conditions with denser snowfall increasing the likelihood for storm slabs during the day due to rising temperatures in and around the 6000' level. Moderate winds were continuing to transport snow onto lee slopes near and above treeline. No deeper instabilities were noted in snowpack tests. Observations were limited in this terrain due to poor visibility. On Sunday in terrain further to the east, a wet loose cycle was noted below 6000'. 

On Saturday, snow professionals at the Barron Yurt near Hart's Pass reported about 6" of new snowfall over the preceding 24 hours. Touchy wind slabs were present near and especially above treeline with moderate to strong W-SW winds transporting new and recent snow onto lee slopes. Storm slabs were generally unlikely to trigger. The 1/16 crust was 4 to 5 feet down. Similar conditions were reported Friday in this area. 

Central

An avalanche professional traveling in Icicle Creek Thursday found 6-8” of settled snow well bonded to the 1/29 crust. Observations demonstrated a strong upper snowpack. No buried surface hoar was found in this location.

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.