Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
4 · Forte
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In sintesi

Expect very dangerous avalanche conditions Sunday with large natural avalanches occurring even at lower elevations. Avoid traveling into, underneath, or near any avalanche paths. 

Problemi valanghivi

  • Wet Slabs

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

    This is not your normal high-hazard day rain event. A substantial amount of cold, layered, dry snow sits at lower elevations. As the rain line moves up the mountains, avalanches will occur. You may see loose wet slides happened first. These avalanches will be dangerous enough on their own. As water drains deeper into the snowpack, several potential pooling layers exist. Large and destructive wet slabs could release from several inches to several feet thick. Stay out of all avalanche terrain, even at lower elevations.

    (12/21/2020) Example: This large wet slab occurred during a rain event earlier this winter.

  • Storm Slabs

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

    Heavy precipitation, warming temperatures, and strong winds will tip the balance in the snowpack Sunday producing large natural avalanches. Many slide paths are well filled in due to the recent snow and resulting avalanche events. This could allow avalanches in this cycle to run far distances reaching near the bottoms of their runout zones. Avoid traveling into or underneath any avalanche terrain on Sunday.

    (2/20/2021) This intentionally triggered storm slab occurred on Saturday near Gold Creek. W, 3800'. SS-ASc-D1-R2-N, 6-8" deep, 20' wide

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    3

    This weather event will significantly test the deeper weak layers in the snowpack. You could see very large natural avalanches occur or storm/wet slabs step-down into older persistent grains. On Saturday a very large avalanche occurred on the mid-January layer near Stevens Pass. This 4-5’ deep slide reminds us that these persistent grains have not gone away. This atmospheric river event could wake them up. If an avalanche fails on these deeper layers, it may result in a slide 6ft or deeper, entrain significant amounts of snow, break trees, and run far distances. Stay well away from large avalanche paths as this storm event unfolds.

    (2/20/2021) This deep avalanche likely failed on the mid-Jan crust Saturday near Stevens Pass. S, 4900' Photo: Wash DOT NCR.

Avalanche Discussion

The avalanche hazard will steadily increase overnight Saturday and into Sunday morning. Eight to twelve inches of snow may accumulate at pass level before the changeover to rain early in the day. This will only add fuel to the fire for any subsequent avalanche events. As the rain line begins to march up the hillside and precipitation ramps up, expect several rounds of natural avalanche activity. If the above problems aren’t enough, Glide avalanche, natural cornices failures, and wind slabs are also on our minds. With so many overlapping, difficult, and dangerous problems this is not the time to try to thread the needle. Let this atmospheric river event playout from a safe location well away from any avalanche terrain. 

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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