Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Strong sun, combined with over 12" of fresh snow on buried crust facet layers mean Friday will be a dangerous day in the mountains. You could trigger large and life threatening avalanches on most aspects and elevations due to this complex snowpack. The riding conditions should be excellent and blue skies will beckon, but keep it dialed back from steeper slopes while the new snow has time to settle. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2

    I would assume all steep slopes near and above treeline have this problem, and you could trigger a life threatening avalanche on or near them. Use low angle slopes for travel, sticking to the high ground. Avoid going underneath larger slopes, as you could trigger avalanches from a distance. Be especially careful near ridgelines and other exposed terrain features that may be recently wind loaded.

    Stay alert to signs of instability in the new snow such as shooting cracks, or whumphing collapses. If you find these, continue to avoid slopes steep enough to slide nearby. Also, just because one slope may have tracks on it does not mean it won't slide on the third of fourth. Unfortunately, this problem won't be going away anytime soon, so we will have to manage terrain selection accordingly. 

    Example persistent slab in the near treeline zone.

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Observers have noted loose avalanches over the past couple of days. Expect wet loose and dry loose avalanches on Friday. Snow could entrain and become large on steep, sustained slopes. You may only have to provoke it, or they could run naturally with sun. Moist, sticky snow and rollerballs are good indicators that wet loose slides could happen spontaneously. Be sure to avoid steep slopes that face the sun directly in the middle of the day to avoid getting avalanched by a slide. 

    Example wet loose avalanche. Photo: Zach McGill

Avalanche Discussion

A forecaster in the Icicle observed whumphing collapses on Thursday above 6,200ft. He identified the problem as faceted grains sandwiched between two crusts under the recent storm snow. I found this same structure on Blewett Pass on Wednesday, and in the upper Chiwawa drainage before the storm. Prior to the snowfall others also noted both near surface facets and surface hoar. Now, we have a slab over this weak structure that appears to be reactive.   

In sheltered areas, you may find twelve to sixteen inches of storm snow over the above mentioned structure. At upper elevations, you may find slightly stiffer and much thicker slabs. Expect to be able to feel the crust underneath in many places, and refrozen chunder from debris or tree bombs could still cause injury.

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.

Regioni coperte