Lawinenlagebericht

Snoqualmie Pass

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

High elevation rain from a potent atmospheric river has drastically changed conditions in the mountains at Snoqualmie Pass. It’s going to take some time for the snowpack to adjust to this load, so limit your exposure to large avalanche paths and ease into terrain carefully as you assess the conditions. Dangerous avalanche conditions will persist even after precipitation has ended on Tuesday.

Lawinenprobleme

  • Wet Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    2–3

    Even as the rain subsides and temperatures slowly cool on Tuesday, our concern for wet avalanches will remain. Copious amounts of liquid water have been introduced to our once dry snowpack at most elevations. This water will continue to test the multiple crusts and layers of weak grains that existed in the upper snowpack prior to this storm. Wet avalanches are difficult to forecast and can sometimes fail hours or even days after precipitation has stopped. Water could be pooling on one of our layers of concerns and slowly breaking the bonds that are holding snow in place. If this happens, the result could be Wet Slab or Glide avalanches large enough to bury and kill you. In specific terrain, these avalanches could grow very large and destructive. Of course, wet loose avalanches will also be present if you venture into the mountains, and these slides could grow large or even trigger lingering slabs as they descend. Your best management tool will be to avoid the runout zone of large avalanche paths, as well as steep slopes over 35 degrees until the snowpack has some more time to adjust to the recent load.

    (2/28/2022)

    WSDOT's avalanche crew reported some of their paths producing natural avalanches up to size D2.5 and hitting the pool down at Franklin Falls.

    Photo: John Stimberis

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    2–3

    At the very highest of elevations, you could find that some peaks escaped the rain and instead received multiple feet of snow. These locations may be hard to find, but if you do, tread lightly near avalanche terrain. The snowpack is certainly still in a state of transition and even if a slope has previously slid, it doesn’t mean that it can’t again. Other slopes may have gotten close to their tipping point and are just waiting for you to come along and push them over the edge. Using test slopes or hand pits probably won’t do the trick with so much snow, so you’re going to need to dig several feet down with your shovel to look at the interfaces and where instability may exist. Your best bet is to stay on slopes under 35 degrees and give the snowpack more time to heal. 

    (12/28/2021)

    The crown of a very large avalanche in the upper Chair Peak Basin earlier this winter.  Similar avalanches may exist at upper elevations. NE-E aspcet, 5800'. SS-N-R2-D2.5-U

    Photo: Dallas Glass

Avalanche Discussion

Rain walloped Snoqualmie Pass as high as the above treeline band on Monday, producing very dangerous avalanche conditions and widespread natural avalanches. As of Monday afternoon, weather stations at the pass have recorded over 6” of water since Saturday night! Observations are limited due to access, but WSDOT’s avalanche team relayed that natural avalanches up to size D2.5 occurred, some of which reached the pool down in Franklin Falls. We expect natural activity to taper on Tuesday, but that doesn’t mean it will be eliminated. And that doesn’t mean that the mountains won’t be dangerous. The rain should continue well into Monday night, continuing to stress the snowpack. On Tuesday, slopes still may not have reached the threshold for producing an avalanche or could reach it for the second or even third time. Yes, peak hazard may have passed by daybreak, which is why we dropped the hazard level, but don’t get complacent thinking that this cycle is over. The snowpack just took on a significant load and wet avalanches are tricky, so we’re not out of the woods yet. Although most slides likely involved the new snow that has fallen since 2/26, the possibility remains for deeper weak layers to produce very large avalanches. We wouldn’t be surprised to hear of one of these happening in the coming days, so ease back into the mountains carefully and manage terrain appropriately.  

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