Boletín de aludes

Snoqualmie Pass

Northwest Avalanche Center
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Peligro de aludes

Thu
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Dangerous avalanche conditions will exist on Wednesday as stormy weather impacts Snoqualmie Pass. Make conservative terrain choices and remember that unsupported slopes, terrain features steeper than 35 degrees, and any slopes with evidence of wind-drifted snow have a higher likelihood of avalanches and should be avoided.

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Expect storm slabs to develop at all elevations as precipitation falls throughout the day Wednesday. Slabs may be deeper and more reactive as you ascend in elevation or where the wind was able to push snow into deeper piles. Look to avoid these deeper piles which are most commonly found on leeward slopes, at the base of cliffs, or on the sides of gullies. Use small test slopes and hand pits to investigate the bond between the new and old snow, along with any interstorm layers that may be present. If you find a poor bond or notice red flag signs of instability such as shooting cracks, collapses, or recent avalanches, then head for slopes less than 35 degrees. 

    (11/25/2020) Test slopes can give you a lot of good information about how new snow has set-up after or during a storm. This test slope shows that storm slabs are sensitive and propagating easily.

Avalanche Discussion

After a couple of days of nice weather, stormy conditions Tuesday night and Wednesday could produce close to 2 feet of snow at Snoqualmie Pass. Prior to this storm, the snowpack around Snoqualmie Pass was defined by an average of 20-35cm of snow sitting over a stout crust (12/21). We saw multiple human triggered avalanches occur in this snow recently but each day seemed to be a step in the right direction of stability. As we prepare for the new snow, keep these recent avalanches in the back of your mind and our previous setup. To add a layer of complexity, weak snow grains were observed on the surface of the snow on Tuesday. It remains to be seen if these grains persist and get buried once the storm hits. If they do, avalanches could break in surprising ways or propagate long distances. It’s our best guess that most avalanches on Wednesday will break at the old/new snow interface, but there remains the possibility that with enough of a rapid load, previous layers could become activated and produce larger avalanches (down to the 12/21). At lower elevations, there will be competing weather influences making for a bit of uncertainty about the possibility of some rain. The snowpack at lower elevations should be well suited to handle rain, but if you find that there is rain falling on fresh snow, Wet Loose avalanches may occur and you should head for lower angled slopes and be aware of terrain above you.

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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