Avalanche forecast

East Slopes South

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
1 · Low
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Out of date — this forecast expired 3 years ago.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

An easterly flow event brought just enough snow to refresh surfaces and build shallow, wind-drifted slabs at upper elevations where you could trigger an avalanche. While these avalanches would 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

    Thin wind slabs at upper elevations may be quite reactive where they formed over weak snow surfaces. They are likely only 4-6 inches deep and in isolated pockets of terrain at the highest elevations. So, while they won't be a significant problem for most backcountry travelers, use caution in extreme terrain where a slip and fall could have high consequences. Likely spots to find these dinner table-sized wind slabs are below sharp ridgelines, at the top of confined gullies, or at the base of cliffs. Textured surfaces, deeper drifts, and cornice formations can also help you identify likely wind slab locations. This new snow fell on various weak and slick surfaces, including large (2-3cm) surface hoar over a thin crust. As you travel through the terrain, monitor how the new snow bonds with the underlying surface using quick hand pits or test slopes. If the snow seems to slide easily, more conservative terrain selection is warranted 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

Even though the surrounding slopes were nearly bare ground, NWAC forecasters in Ahtanum Meadows were pleasantly surprised by enough snow for groomed trails from the snowpark. Continuous coverage off of the roads began 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. 

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 snow sandwiched in between. A layer of surface hoar buried 20-30cm deep produced unstable test results. Tuesday's storm buried another layer of surface hoar 2-4 inches deep. We'll continue to track these weak layers as snow accumulates and a cohesive slab forms. 

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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