Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

New snow and wind will continue to build fresh slabs in exposed areas and rocky features at mid and upper elevations. While blowing snow may be the in-your-face issue, lingering uncertainty around older layers should stay on your mind. Avoid traveling under large unsupported slopes where these bigger avalanches could still occur.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Moderate winds should continue to build a fresh round of winds slabs along exposed ridgelines and near rocky features Wednesday. You may find wind-drifted slabs below cornices, in the tops of chutes, or along the base of cliffs. Anticipate wind-loaded areas where you see blowing snow loading lee slopes. Steer around the pillow-like slabs by using scoured or lower-angled slopes.

    On Tuesday, small natural wind slabs were observed in the Washington Pass areas. Many of these slides occurred in more rocky alpine features. You could see similar conditions Wednesday.

    (1/17/2023)

    Natural wind slab avalanches near the base of cliffs. 

    Photo: Katie Warren

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1.5–2.5

    While this isn’t a very big storm, additional snow and wind loading could continue to stress older weak layers in the snowpack. Put plenty of space between you and large unsupported startzones that could still produce these more unpredictable slides. We’re still concerned about the 1/5 surface hoar layer frequently found about 2ft below the snow surface. A trickle of avalanche observations including a very large slide that occurred in Liberty Bowl a few days ago continues to emphasize that this layer hasn’t fully gone away. You’re most likely to find it in wind-sheltered terrain and around areas with sparse trees. Snowpack tests from local professionals have produced harder results, but the structure remains largely intact. If you experience shooting cracks or feel collapses, seek out terrain away from large steep slopes.

    (1/17/2023)

    A large avalanche in Liberty Bowl. NNW 7600ft. Snow on the debris indicates this slide is a few days old. It is believed to have stepped down to the 1/5 interface. 

    Photo: North Cascades Heli

Avalanche Discussion

Observations from Tuesday continued to demonstrate the ground-hog-day pattern we seem to find ourselves in. An avalanche professional traveling in the Washington Pass area reported wind-affected snow and small natural wind slabs. While not a recent avalanche, the larger slide in Liberty Bowl is thought to have stepped down to the 1/5 surface hoar layer. In both cases, these observations highlight the continued set of avalanche problems you will face. 

On Monday, observers at 6,200ft, NW in the Hairpin valley reported sudden and propagating test results on the Jan 5th surface hoar, 2 feet (70cm) below the surface. The results were very hard (beyond the limits of standard tests) and the surface hoar was small and rounding (0.5mm). They also reported moist snow, but no crust in the upper layers. 

This all comes on the heels of a more widespread avalanche cycle late last week that even involved wet avalanches down into the lowlands. Several of these lower elevation wet slides ran on or near the ground. Now frozen piles of debris litter the hillsides.

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