Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Slab avalanches may be large at all elevations on Wednesday, but wind may create thicker and more dangerous avalanches the higher you go. Deeper weak layers may be reactive in areas with a shallow snowpack, such as the eastern edge of the zone. Steer clear of steep open slopes while the snowpack adjusts to the new load.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    By Wednesday, approximately 30" of new snow will have fallen since the new year. Steer around steep slopes while the snowpack adjusts to this hefty new load. You could trigger a large slab avalanche within the recent storm layers. Slabs could be deeper and thickened by wind at mid and upper elevations. Be careful around cornices on ridgelines, as they could be very touchy. Look for signs of instability such as shooting cracks or whumphing collapses. Places such as steep, convex rollovers and unsupported slopes will be the easiest places to trigger a slab within the new snow. 

    Loose dry avalanches may be easy to initiate in the deep snow. Look for these fan-shaped slides that start from a point (also known as point releases). In steep terrain, these could entrain lots of snow, and create large avalanches. 

     

    (1/2/2021) Storm slab in nearby East Central Zone.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Persistent slab avalanches may begin to 'wake up' with continued loading from recent storms. A weak layer of sugary snow sits atop, or below a thin icy crust from early December. Keep this deeper layer at the top of your mind at mid elevations and further east where the snowpack is more shallow. In most areas near the crest, this layer has already undergone a substantial avalanche cycle, and may not be a problem anymore. As you travel, assess for signs of instability like recent avalanches, whumphing collapses, and shooting cracks. The next couple of days will be a good time to stay off of steep, open slopes as storms continue to stress these deep weak layers. The most dangerous slopes will be mid elevation, unsuspecting slopes in sparse trees, and large open starting zones in the eastern edge of the zone where the snowpack was less than 3ft deep before the new year.

    1/5/2021: Example persistent slab failing on weak snow over a crust in the Wenatchee Mountains.

Avalanche Discussion

An observer found moderate wind drifting near ridgetop in Cutthroat Drainage on Tuesday, and mostly stable snow below treeline. Observers in Holden Village reported a few natural D2's from Tuesday's storm, running from alpine features into the upper runout zones from a south facing ridgeline. On Monday, observers reported trees collapsing under the weight of the heavy new snow up Cutthroat Drainage. The storm produced significant accumulations for the mountains north and east of Winthrop, and may stress deeper weak layers there. Sunday, an observer reported an isolated whumph near a windloaded ridgeline at 6,800ft in the Cutthroat Drainage. A observer in the Twisp River found ongoing wind transport in the alpine throughout the day. Digging down on a SW aspect at 5,800ft, he got sudden collapse test results down 75cm on the Early December Crust. Other recent snowpack tests showed that propagation was possible on this interface about 2 ft down at around 5700' on Driveway Butte. 

Deep snow immersion is real out there. Be vigilant around tree wells and stay close to a partner while traveling through the trees. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources. Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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