Lawinenlagebericht

Snoqualmie Pass

Northwest Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Fri
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

You’ll need to balance changing conditions as the weather and the snowpack transition from a winter storm to warmer temperatures and periods of sunshine throughout the day. Choose routes with plenty of options to avoid steep slopes and adapt to the variable conditions.

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    A winter storm should continue to impact the Snoqualmie area Wednesday night with a few isolated showers Thursday morning. By the time the precipitation stops, storm totals at mid-elevations could easily exceed one foot. High precipitation rates, warming temperatures, and strong winds during the storm likely formed several interfaces that could produce avalanches. Use small slopes and handpits to observe the new snow and look for layers that may fail. You may trigger slabs on very steep slopes, near convex rollovers, around rocky terrain, or in wind-affected snow. Expect deeper and larger avalanches at upper elevations and in wind loaded areas. 

    At lower elevations, warmer temperatures resulted in less snow accumulation. We anticipate slabs in this band to generally be thinner and harder to trigger. As you begin to ascend and find deeper, drier snow, recognize conditions have changed and you may need a more conservative approach.

    (11/25/2020) Example: Small low consequence test slopes like this can provide information about the new snow's ability to fail and produce avalanches.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    One of the most important parts of Thursday’s transition involves the sky. Predicting cloud cover is exceptionally challenging this time of year. Different parts of the Snoqualmie zone could experience very different amounts of sunshine throughout the day. Locations east of the Pass stand the highest chance of seeing significant sun breaks. If you notice the sky beginning to thin or see patches of sun, think natural Loose Wet avalanches. You may not need blue sky to begin to experience these conditions. Filtered sunshine and “greenhousing” maybe all that’s need to warm the snow and initiate this avalanche problem. Wet sticky snow surfaces, the snow shedding from trees, and new rollerballs often serve as precursors for avalanche activity and should indicate to you the surface is becoming unstable. When you see these clues, seek out more shaded slopes or lower angled terrain. 

    (3/23/2021) Natural loose wet avalanches occurred on Tuesday when periods of sunshine caused the snow surface to become wet and unstable.

Avalanche Discussion

As of Wednesday afternoon, 6-10” of snow had accumulated around Snoqualmie Pass. An additional 3-4” could fall during the afternoon and evening. Moderate to strong SW winds and warming temperatures accompanied much of this snowfall and likely formed an upside-down upper snowpack. This snow sits above a new interface (3/24). Prior to the storm, a wide variety of surfaces were found including firm crusts, weak snow, and settled powder. As a result, you may find that the upper snowpack reacts very differently from one slope to the next. If avalanches fail on the firm crust or pockets of weak snow, they may trigger very easily and run fast.  Despite this high level of variability, we believe that avalanche concerns will remain above this latest interface.

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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