Bollettino valanghe

Olympics

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Stormy weather and a buried weak layer of snow could make conditions particularly dangerous Saturday in the Olympics. Don’t treat this like a run-of-the-mill storm day. Give any steep open slope a wide berth.

Problemi valanghivi

  • Wind Slabs

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

    Strong and gusty winds will continue to scour ridgelines and load leeward slopes. As a result, you may encounter wind slabs well below ridgelines and on cross-loaded gullies. Pay particular attention near exposed features, along the base of cliffs, and in confined chutes where the wind often deposits snow. Sharp cornices, blowing snow, and drifts behind rock/trees can help you avoid these steep wind-loaded areas.

    A buried layer of surface hoar may hide under some of these wind slabs and make them very easy to trigger. This won’t be the day to try to thread your way around wind-loaded pockets. If these stiffer slabs sit on these buried persistent grains, you may trigger them remotely or from lower on the slope.

    (12/9/2022)

    Blowing snow and drifts highlight potentially wind loaded areas. 

    Photo: Sam Luthy Siemens

  • Storm Slabs

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

    Even though you’re out of the wind doesn’t mean you’re out of danger. While the snow totals from this storm might not impress you, avalanches may fail from the new snow. Use hand pits, uptrack tests, and small slopes to see how the new snow reacts and if it bonded to the old surface. If you find the new snow cracks or fails easily, steer away from steep open slopes. 

    This new snow could also begin to push any buried surface hoar to its breaking point. These avalanches would involve not just the new storm snow, but all the snow above this weak layer. Slides could easily be 2 ft or more deep. This might even include natural avalanches, remotely triggered slides, or cracking/collapsing. As we said, this may not be your run-of-the-mill storm day. Let this storm play out well away from any steep open slope.

    (12/8/2022)

    Buried surface hoar was even found in shallower snowpacks on more wind stripped aspects. 

    Photo: Sam Luthy Siemens

Avalanche Discussion

While this will certainly not be the biggest winter storm the Olympics will see all year, the unique combination of strong winds, significant snow, and a possibly buried weak layer should catch your attention. A foot of snow could accumulate at Hurrican Ridge by the time precipitation starts to wane Saturday afternoon. 

Observations from NPS staff and backcountry professionals Thursday and Friday continue to report buried surface hoar on all aspects around Hurricane Ridge. Prior to this storm, this weak snow sat 4-12in below the surface. So far, these persistent grains have not produced any known avalanches. That could change with additional snow. Not surprisingly, these same observers also reported wind-scoured ridges and small cornices in many locations. 

Even though it may look and feel a lot like winter, open creeks, holes near rocks, and shallowly buried trees still abound. Give yourself time to navigate these early season obstacles.

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