Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

This storm will likely create dangerous avalanche conditions at the Pass Sunday. As a result, you may trigger avalanches on a variety of steep slopes. So, choose simple, low consequence terrain that allows you easily identify and avoid open areas greater than 35 degrees. 

Problemi valanghivi

  • Storm Slabs

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

    While this isn’t a huge storm, it should bring significant snowfall over a relatively short amount of time to the Pass. This will certainly result in an increase in the danger, but pinning down exactly what type of avalanche is a little harder. As a result, be leery of all open slopes greater than 35 degrees. 

    Much of the danger will depend on how the new snow bonds to the old surface. Unfortunately, variable conditions were widely reported across the zone on Saturday. This could mean each slope responds differently. So, while hand pits, up track tests, and small slopes will give you an insight into this bonding, they may not represent the next opening in front of you. When conditions get tricky like this, low consequence, easy to manage terrain is a great answer. 

    You may encounter storm slabs, wind slabs, and loose dry avalanches throughout your day. Expect the largest and most dangerous slides at mid and upper elevation, particularly where you see the wind blowing snow into deeper and firmer slabs.

    (12/20/2022)

    An example of a small storm slab. 

    Photo: Public Observation

Avalanche Discussion

The stormy conditions Sunday will be pretty obvious, but don’t forget how that may impact the avalanche danger over short periods of time. You could find that avalanches trigger very easily (or fail naturally) during or immediately after intense snow showers and stronger winds. 

On Saturday a wide variety of snow surfaces were reported including wind textures, firm crust, soft powder, and weak grains (faces and surface hoar). Fortunately, these pockets of weak snow were localized which should help limit their ability to cause bigger avalanches. As we mentioned, this could cause the snow to act differently from one slope to the next. It also means you could see some avalanches run far and fast over those firm older surfaces. 

While we think most of the avalanche activity will occur at or above the new/old interface, we can’t rule out a few isolated slides breaking into older snow. It's been an active few days at the Pass with several natural and human-triggered avalanches. We wouldn’t be surprised for a few of these slides to either step down into older snow (2/19) or release a lingering wind-loaded pocket. 

On Saturday an NWAC forecaster traveled up the Alpental Valley to take a look at several of these recent avalanches. Crowns from natural wind slabs (Thursday) and human-triggered slides (Friday) were abundant on NW-N-NE facing terrain at mid and upper elevations. One of these slides caught and carried a tourer over a cliff down towards Snow Lake. He sustained significant injuries and was evacuated by King County Sheriff’s Medic One Helicopter. 

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