Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Happy New Year! If you don’t want to see the kind of avalanche fireworks the backcountry can produce, stay off of open slopes greater than 35 degrees. Recently formed storm slabs need time to heal at mid and upper elevations. Below the rain-snow line, you could encounter wet heavy snow that may avalanche on very steep slopes.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Numerous natural and triggered avalanches occurred around Snoqualmie Pass Thursday. While the bulk of the natural avalanche activity may have ended, slabs can still fail under your weight. Give these storm snow layers more time to gain strength by staying away from steep open terrain. You can use small slope tests and hand pits to look at potential weak layers close to the surface. However, with more than 2’ of recent snow, it will be hard to assess all the potential weaknesses without using your shovel. Pay particular attention to the most recent interface (12/29). In nearby zones, this served as the bed surface for a few avalanches. Avalanches may trigger more easily in very steep and rocky terrain and in locations the wind drifted the snow deeper. 

    Prior to this storm surface hoar was reported in many areas. We do not know if it was buried intact at Snoqualmie Pass. Avalanches breaking on this layer would be 2 or more feet deep and could fail in surprising ways. If you see evidence of this layer, please let us know by submitting an observation.

    (12/31/2020) A human triggered avalanche near Kendall Peak in the Snoqualmie Pass area. This avalanche failed on a relatively low angled slope.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Warm temperatures and a little rain are expected well into the near treeline band around the Pass Friday. Fortunately, the relatively modest expected rain totals should help minimize any avalanche activity. However, when rain falls on cold dry snow it’s time to pay attention. We’re most worried about rain on snow at mid-elevations that remained as cold and dry Thursday. If you see new rollerballs or find the snow surface becoming wet and heavy, steer around steep open slopes. We suspect wet avalanches may be hard to trigger, but once they get moving they may entrain the recent snow and become large. 

    At lower elevations, rain from Thursday should limit the impact of additional water on the snowpack.

    (11/27/2020) Example: Rollerballs like this are great clues that the snow surface is becoming wet and unstable.

Avalanche Discussion

The snowpack at Snoqualmie Pass continues to grow deeper. The Pass received more than 3.5” of precipitation since this storm began on 12/29 resulting in  2’ of snow at the road level and more at higher elevations. Oscillating temperatures and strong winds formed new cornices along ridgelines. These fresh deposits could trigger easily. Give them a wide berth and anticipate cornices failing further back than you expect. 

Happy New Year from all of us at NWAC!

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