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 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Stormy weather continues to impact Snoqualmie Pass maintaining dangerous avalanche conditions. Keep things simple Saturday and steer around any open slope greater than 35 degrees. As you ascend in elevation, expect larger and more dangerous avalanches.

Problemi valanghivi

  • Storm Slabs

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

    After more than a week of storms, mid and upper elevations around the Pass have lots of snow. A mild and wet system Friday night into the wee hours of Saturday could add an additional 8-12 inches. Relatively warm temperatures, intense precipitation rates, and strong winds should easily build storm slabs on any open slope not directly stripped by the wind. Choose easy to navigate terrain Saturday and steer around all open slopes greater than 35 degrees. We expect natural avalanche activity to occur during the heavy precipitation Friday night. However, don’t rule out the possibility of a natural avalanche during the day, particularly if you observe the wind still blowing snow on the ridgelines. This won’t be a day to hang out in places where avalanche may run or stop. Use small slopes and hand pits to gather information about which storm layers fail and how they may react to your weight. 

    About 4” (10cm) above a prominent crust (12/09) observations continue to find small facets and buried surface hoar. So far, we have not confirmed any avalanches on these persistent grains at Snoqualmie Pass. However, several avalanches occurred on this layer at nearby Stevens Pass. At this point, this layer is deep (2-4’ 60-120cm) and any avalanche would be very large and destructive. Uncertainty surrounding this layer continues to weigh on our minds. Consider limiting your exposure to large avalanche terrain especially at mid-elevations as storms continue to test this weak layer. 

    (12/18/2020) This snow profile shows how much snow lies over the 12/09 crust (blue card). Each layer of snow above indicates the most impactful recent storms.

Avalanche Discussion

Don’t be surprised if you see a few new debris piles from a Friday night avalanche cycle. Drier weather Saturday should very slowly give the snowpack time to adjust to its new load. This active weather week continues to stress the snowpack and so far Snoqualmie Pass has not seen a widespread avalanche cycle.  One has to wonder if this storm will push us past that tipping point. Meanwhile, lower elevations continue to take a beating limiting the avalanche hazard. More rain and heavy wet snow will maintain a slight chance for small loose wet avalanches near Pass level and below. If you see new rollerballs or fan-shaped debris stay away from similar slopes. 

Our next system arrives Saturday evening. This particular storm looks very large and may significantly increase avalanche danger. We don't often talk about the Day 2 outlook, but the possibility for very dangerous conditions to develop has our attention. Travel in the backcountry Saturday night is not recommended. 

Even with all the recent snow, lower elevations continue to hold early-season travel conditions. Anticipate wet heavy snow, open creeks, thin coverage, and plenty of obstacles to navigate. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could

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