Bulletin d’avalanche

East Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Sat
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Dangerous avalanche conditions exist in the Wenatchee Mountains where there have been very large, recent avalanches. Avoid slopes 35 degrees and steeper above treeline, especially where you find either recently drifted snow or older weak layers of snow. Watch for signs that you could trigger a large and deadly avalanche such as whumphing collapses, cracks shooting through the snow, and other recent avalanches.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    You can trigger very large and destructive avalanches in the Wenatchee Mountains and anywhere with less than five feet of snow on the ground. You may even be able to trigger these avalanches from far away. Persistent slab avalanches can break widely across terrain features and can be very surprising. Stay far away from and out from under slopes 35 degrees and steeper. Make sure to stop and re-group in areas well away from avalanche terrain. Consider avoiding avalanche terrain altogether. Use extra caution on slopes where you see wind drifted snow or slopes that are thickly covered by recent snowfall.

    Up to 3 feet of recent snow fell since Dec 30th. In the Wenatchee Mountains, you can find this resting on weak, old layers of snow. The weak snow will look loose, sugar-like, and granular. You may find old crusts near the weak snow, as well. Persistent Slab avalanches are most prevalent in the Wenatchee Mountains and the far eastern edge of the Cascades. Closer to the Cascade crest, it's less likely that you'll trigger these dangerous avalanches, though not impossible. Anywhere that you find the new snow resting on old, weak layers you may be able to trigger an avalanche.

    (1/6/2021) Explosive triggered hard slab avalanche at Mission Ridge. Photo Jake Larson

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1

    You can trigger avalanches on leeward, wind-loaded slopes near and above treeline. East and southeast winds may be strong enough to build fresh slabs on an already weak snowpack. Cornices, wind features, and firm wind-stiffened snow are all signs that the wind has drifted snow. Watch for signs that you could trigger an avalanche such as cracks shooting through the snow and other recent avalanches. Use extra caution near wind-loaded slopes as triggering a wind slab could result in a much larger and deadly persistent slab avalanche. Cornices have become large. Make sure to keep your distance by staying off of them and don't linger under them. 

    (12/31/2020)An example of wind features (foreground right) from a wind event in late December on Washington Pass. Photo: Josh Hirshberg

Avalanche Discussion

The past week has brought dynamic storms and lots of avalanche activity. In addition to the avalanches mentioned above, you may encounter small loose avalanches on steep, wind-sheltered slopes. Many areas near the Cascade crest hold very deep snow from the past week. Be aware of the risk of falling in tree wells, deep snow immersion, and falling tree bombs. Currently, there's a big variation in snowpack characteristics in the zone. You can find a deeper, stronger snowpack near the Cascade crest, where it's difficult to trigger avalanches in older weak layers. Further east the snowpack remains weak and shallow.

An observer near Holden village reported fresh loose avalanches on Thursday along with slab avalanches (to size D3) from earlier this week. Observers in the icicle drainage reported a very large (D3) avalanche that ran in Big Slide creek earlier this week. On Thursday, an observer in the Wenatchee Mountains reported surface hoar on the snow surface and test results indicating that you could still trigger avalanches on facets over the December 21st crust. Mission Ridge Ski Patrol triggered very large avalanches with explosives on NE aspects around 6,300ft on Wednesday. These slides involved most of the season's snowpack and ran on old weak layers. An observer on Blewett Pass reported a natural size D3 avalanche that likely ran Tuesday night near Diamond Head. 

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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