Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Expect increasing danger during the day as snowfall accumulates, and temperatures gradually warm up. In the lower elevation foothills and eastern part of the zone, slabs may break in surprising ways if they sit over weak snow near the ground. Stay off of steep slopes if you find more than 8" of new snow, or signs of danger such as shooting cracks or whumphing collapses.

Avalanche problems

  • Storm Slabs

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

    A warm storm is expected to create storm slab instabilities for the next couple of days. Temperatures should slowly warm up during the day, and the new snow may become heavier on top. This may make it easy to trigger slab avalanches in the new snow, or on old interfaces. Look for signs of instabilities such as shooting cracks and fresh, natural avalanches on steep open terrain. Avoid areas that are actively being loaded by the wind, and avoid cornices. Stay out from underneath large, steep features that may shed storm snow during times of heavy snowfall.

    In the eastern foothills such as the Twisp Valley, whumphing and cracking were reported after strong winds built slabs over a weak and shallow snowpack. Several recent natural slab avalanches were observed in this lowland, grassy terrain.  Stick to slopes lower than 30 degrees if you experience whumphing while traveling at lower elevations or see recent avalanches on similar slopes.

    Roofs continue to pose a hazard due to the deep snow from recent storms. Stay away from the impact zone for potential roof avalanches. 

    Example storm slab from earlier this season.

    Photo: Adam Butterfield

Avalanche Discussion

Expect a fairly stormy day with dense, new snow and rising freezing levels. Danger will increase as the day progresses, and conditions should only become more dangerous overnight into Wednesday as more snow accumulates and temperatures continue to warm. On Monday, observers in the greater Washington Pass area found mostly stable conditions with lingering concerns for wind slabs at higher elevations. Pockets of surface hoar were noted, and likely exist in other areas to some extent. A thin crust had developed on the surface of steep south-facing slopes, and a fairly stout crust was found below 6" of dry snow up to around 5,300ft. 

The last storm wrapped up on the 7th in the Hwy 20 corridor, and observers noted a widespread cycle with avalanches up to D2.5.  Slab avalanches were reported at low elevations in the eastern part of the zone including the Methow Valley and Twisp Valley.  A widespread cycle also occurred at lower elevations and in sagebrush country in the East Central zone, including in places like along Hwy 97A above the Columbia River.  Check out some of the amazing photos below and additional information in the East Central forecast.   In the Washington Pass area,  roughly 3.3 inches of water was recorded over this stretch with 2' of settling storm snow.  Mazama saw 18" over this period.  The storm ended with rapid cooling and extreme westerly winds that transported significant snow at all elevations on Friday.  

Regions covered