Bulletin d’avalanche

Stevens Pass

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

Expect to find shallow, reactive wind slabs in upper elevation terrain. Steer around drifted or wind textured snow on steeper slopes. Firm and icy travel conditions may be found in the trees and at low elevations.

Problèmes avalancheux

  • Wind Slabs

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

    There may be just enough new snow and wind to create shallow, reactive wind slabs in upper elevation terrain. These should be fairly small, but may be easily triggered as they could rest over firm, old snow surfaces. Steer around areas that appear loaded and deeper on steep and consequential slopes. You can use small, wind loaded test slopes to check how the new snow is bonding to older surfaces. 

    If the sun comes out, watch out for small loose wet avalanches on very steep slopes. Look for signs such as moist, sticky snow and rollerballs. Avoid steep slopes, or terrain with heightened consequences if you notice fresh loose wet avalanches on nearby slopes. 

    Example wind textured snow from March 8th in White Pine Cirque.

Avalanche Discussion

We could pick up 4-6" if a Puget Sound Convergence Zone sets up over the area on Sunday night. Expect more snow at upper elevations and west of the pass, where snowfall will accumulate more readily. It's mid March, and if the sun does come out, expect it to quickly moisten the snow surfaces. The new snow will be falling on well-developed crusts on east to west to south aspects and all aspects at lower elevation. On north facing slopes at upper elevation, it will fall on weaker, near-surface faceted grains. Observers reported cornice fall last week, and more recently in other zones. Observers have also reported glide cracks opening and ongoing loose wet avalanches on sun-exposed slopes. 

While deep persistent slab avalanches are dormant and unlikely, the snowpack structure can still be found. The mid-January crust-facet layer is now 8-9 feet below the surface and showing signs of strengthening. Drainages far east of the pass and into the East Central zone are more prone to these avalanches. The last known deep slab avalanche in this zone was on March 1 with another suspected in the West South zone on March 3. Major warming events later in spring and summer could trigger further rounds of avalanches on this layer. Keep in mind the consequences of these massive avalanches and give yourself an extra margin of terrain in and around large avalanche paths.

On March 1st, WSDOT avalanche teams triggered an 8ft deep D3 avalanche on the southeast face of Rock Mountain east of Stevens Pass. In the Chiwaukum Mountains, a natural D3.5 avalanche in upper-elevation north-facing terrain is suspected to have run on the 28th. A massive avalanche (D4) ran naturally in the West Camp path on Rock Mountain less than 2 weeks ago. These are just a few of the very large and historic avalanches that occurred in the second half of February.

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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