Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Expect slab avalanches to occur in the last 24 hours’ snowfall. This new layer may not bond well to the layer beneath it, so avalanches could run easily. Check the interface between the layers and test small slopes before heading out onto large slopes steeper than 35 degrees.

Problemi valanghivi

  • Wind Slabs

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

    Wednesday night’s snow fell on a thick crust in many areas, which you may find is an excellent bed surface for avalanches. The case is different on northerly slopes above approximately 5500 feet where dry low density snow was present on the surface. Weak snow crystals in that snow were documented on Tuesday, so slabs may easily run on that interface as well.

    Areas where wind redistributed the snow into thicker, stiffer slabs and poor bonding to the underlying layer are a great recipe for triggering avalanches. You might find slabs very soft and hardly noticeable compared to other swaths of nearby snow. Depending on how weak the interface is, the storm snow alone may form enough of a slab to avalanche with the addition of a human trigger. In non wind-affected areas this low density snow may also “sluff” as small, loose avalanches. 

    Investigate conditions as you travel. The new layer is shallow enough that you can dig down with your hand to the crust beneath and isolate a column of new snow, pulling on the back wall to determine if it easily pops off the underlying layer (check out the video below).  If you find the layer easily popping off, that’s a good reason to avoid steep slopes. These conditions work well for using small test slopes  to see if you can trigger an avalanche.  Until you’ve done a number of assessments, stay off slopes steeper than 35 degrees.

    A slab avalanche which occurred a couple weeks ago on a new/old snow interface in the West North zone, similar to what we might see on Thursday.

Avalanche Discussion

There is a possibility that the sun could break through the clouds in the afternoon.  If this is the case, the strong spring sunshine could cause wet loose avalanches on steep sunny slopes. Conditions change quickly in this fickle spring weather. The fresh powder is a drastic change from earlier this week, so stay alert as slab avalanches pose a greater threat once again.  

You will find hard underlying crusts on all lower elevation aspects and the east, south, and west at upper elevations as well. In areas where it is smooth the crust could provide a slick bed surface, but in many steep areas rollerballs and wet loose avalanches already came down, roughing up the surface. It might make triggering avalanches a bit more difficult, but it could also cause injury if you encounter hidden hard chunks beneath the fresh snow.

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.

Regioni coperte