Bulletin d’avalanche

Stevens Pass

Northwest Avalanche Center
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Danger d’avalanche

Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You can trigger slab avalanches in the 6+ inches of snow that falls Wednesday night. Travel cautiously in areas greater than 35 degrees, and test small slopes to determine how reactive the snow is before getting out on larger slopes. Patches of afternoon sunlight might warm snow enough to cause small wet loose avalanches, so if you notice snow getting wet steer clear of steep slopes nearby.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    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 skier triggered D1 slab avalanche near Tye Peak from a few weeks ago. It ran on the storm snow interface. This is very similar to what you might see on Thursday.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1

    If we get afternoon cloud breaks, lower elevation areas on the southern half where low density snow exists will quickly moisten and begin to avalanche. With intense spring sun, it does not take long for this transition to occur, so keep this in mind as you travel. Pay attention to sky cover and snow conditions, and if snow surfaces begin getting moist or you see rollerballs running downslope retreat to shadier areas or low angle terrain. 

    An example of recent small, natural wet loose avalanches and rollerballs running in the new snow.

Avalanche Discussion

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.

Conditions drastically changed from earlier this week. The powder will be a welcome change, but stay alert as slab avalanches pose a greater threat once again.  

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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