Bollettino valanghe

Snoqualmie Pass

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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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

This may not seem like a very big storm for the Pass, but new snow, shifting winds, and recent human-triggered avalanches all point towards dangerous conditions developing. Give the snowpack time to heal by avoiding all steep open slopes, particularly at mid and upper elevations.

Problemi valanghivi

  • Storm Slabs

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

    Shallow storm slabs could form overnight with higher precipitation rates and gradually warming temperatures. You could easily trigger these smaller avalanches, especially in the morning when they are fresh. Hand pits, uptrack tests, and small slopes can all give you information on how the new snow may react. If you see it fails easily or cracks, then steer away from nearby steep slopes. In wind-affected areas, you may find slightly firmer and deeper slabs that could produce larger avalanches. 

    On Friday backcountry travelers trigger several smaller slab avalanches in the Alpental Valley. These 8in deep slides likely failed on the 12/8 interface. In neighboring zones, buried surface hoar was found at this layer. While we have no observations of buried surface hoar around Snoqualmie Pass, it’s obviously on our minds. If it exists, storm slabs could trigger easily, involve more snow, and grow larger. Unfortunately, it may be nearly impossible to tell which slopes hold this hidden beast. Given the potential complexity, recently triggered avalanches, and ongoing storm, Saturday could be a good day to seek out lower-angled and/or treed terrain.

    (12/9/2022)

    These two skier triggered avalanches failed in the Alpental Valley Friday 12/9. N-NE, 4500ft, SS-AS-D1-R1-U

Avalanche Discussion

This storm track doesn’t favor Snoqualmie Pass. Even still we could easily see 8-10in of new snow before the showers starts to taper off Saturday afternoon. Normally you might not find dangerous conditions with these modest storm totals. However, this unique storm track, prolonged cold weather, and a potentially buried persistent weak layer all point us toward dangerous conditions, especially in the morning near the peak of the storm. 

NWAC forecasters and avalanche professionals observed a buried surface hoar Friday in the Stevens Pass, West South, Olympics, and Mt Hood zones. This layer of weak feather grains was typically found 8-15in below the surface prior to the new snow. Commonly across all these areas, this weak layer failed in tests but had not yet produced any avalanches. We do not know if it formed at Snoqualmie Pass. However, the human-triggered avalanches in Alpental Valley make us very curious. 

Even though it looks and feels a lot like winter, early-season conditions still exist. Don’t let your excitement for the soft snow carry you into open creeks, holes near rocks, or shallowly buried trees.

Regioni coperte