Avalanche forecast

East Slopes South

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Winds will increase overnight on Wednesday, drifting the recent snow into stiff slabs where you could trigger an avalanche. While these avalanches will likely be small, they could be easy to trigger and have high consequences in extreme terrain. Stick to lower-angle slopes if you observe shooting cracks or whumphing collapses. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Increasing winds will drift the recent snow into more cohesive wind slabs on lee aspects. They may be quite reactive where they formed over weak snow surfaces. Wind slabs will likely be shallow and isolated to mid and upper elevations with a more consistent snowpack. While they won't be a significant hazard for most backcountry travelers, use caution in extreme terrain where a slip and fall could have high consequences. Likely spots to find these small wind slabs are below sharp ridgelines, at the top of confined gullies, or the base of cliffs. Textured surfaces, deeper drifts, and cornice formations can also help you identify likely wind slab locations. 

    Recent snow totals vary throughout the zone, and new snow fell on various weak and slick surfaces, including surface hoar, faceted snow, and melt-freeze crusts. As you travel through the terrain, monitor the new snow depths and how the new snow bonds with the underlying surface using quick hand pits or test slopes. If you find more than 6-8 inches of snow that slides easily on older layers, choose more conservative terrain to prevent getting surprised by a small avalanche.

    (1/2/2024)

    You can use small wind drifts to test the reactivity of any wind slabs like in this example. 

Avalanche Discussion

A storm favoring the eastern Cascades brought 4-6 inches of snow to the East South zone. This new snow buried weak old surfaces, consisting of surface hoar and facets over a thin crust (1/2 SH). This new interface showed signs of reactivity in snowpack tests in East Central on Wednesday. While not much of a slab exists over this layer yet, as the week progresses, we will be in a "trickle-in" weather pattern with light snow and increasing winds. Additional snow will progressively build more of a slab on top of these suspect weak layers, so expect a slow and steady increase in the avalanche danger. As we approach the weekend, a more robust storm system may be quicker to overload these layers. 

The base of the snowpack is a layer of weak snow capped by a thick layer of hard, refrozen melt forms. The upper snowpack is a mix of melt-freeze crusts with weak snow sandwiched in between and a layer of surface hoar, buried 20-30cm deep, which produced unstable test results. So, as we gradually build a more robust slab over these weaknesses, approach new terrain slowly and carefully monitor how well the new snow bonds with the old surface. Quick hand pits, test slopes, and shovel tilt tests are great ways to identify weak layers with soft storm snow. Be particularly suspicious of lee slopes below ridges, the base of cliffs, and confined alpine features where winds quickly sift snow into stiff slabs faster than in sheltered terrain. 

NWAC forecasters were out in Ahtanum Meadows on Tuesday. The roads were snow-covered and groomed from the snowpark, but continuous coverage off-trail did not begin until around Colver Flats (6200ft). Up near Darland Mountain, snow depths were between 2-3ft. Unfortunately, southern aspects are the exception, and they have melted back significantly with lots of ground showing. 

Early season conditions still exist across much of the zone. Look for hidden hazards such as downed trees, stumps, creeks, and rocks. 

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