Bulletin d’avalanche

Stevens Pass

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

On the heels of a big storm, Monday will bring sunny skies and moderate temperatures. You can trigger avalanches, some big enough to injure or kill you, where the wind drifted stiffer slabs of snow onto steep slopes just below ridges. To avoid these avalanches, you can stick to wind-sheltered terrain and slopes less than 35 degrees. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Avalanches will be bigger and easier to trigger at upper elevations. While they may be smaller, you can still trigger them at middle elevations. As the winds have tapered off, you'll need to look for clues on leeward slopes where you can trigger avalanches. Look for avalanches, shooting cracks, and stiffer pillows of drifted snow to indicate the danger. Use small test slopes to assess the snowpack before comitting to larger terrain. If you see signs of instability or drifting, stick to lower-angle slopes or wind-sheltered terrain.

    (12/8/2024)

    A skier triggered avalanche (D1) in the top 20cm of recently drifted storm snow. Mill Creek, SE, 5,300ft

    Photo: Josh Hirshberg

Avalanche Discussion

The low, weak sun may be able to barely warm snow surfaces on steep south aspects. We don't expect consequential wet avalanches, but it's a good idea to watch for rollerballs as signs of wet instability.

On Sunday, an NWAC forecaster on Stevens Pass found 1 foot of recent snow at low elevations and drifts of 20-28" on mid-elevation ridges. They triggered  avalanches on a couple small wind-loaded test slopes. The crowns were 8-10" deep, and the slides ran until slope angles dropped below 35 degrees. During avalanche mitigation work, Stevens Pass ski patrol triggered numerous small avalanches, up to size D1.5, in steep terrain around 5,500ft. These were all running within the top portion of the new snow. 

From December 7-8th, a major storm brought just under 2" of water equivilent to the Stevens Pass area. The first half fell as rain, wetting the old snow and likely destroying the host of weak layers. Below about 4,700ft, you can find the 12/7 interface still moist and unfrozen under about a foot of new snow. As you go up in elevations, you'll find more new snow and that the 12/7 crust is harder and frozen. Generally, the new snow is "right side up," progressively harder with depth, and well-bonded to the 12/7 interface.

 

Please let us know what you see in the mountains by submitting an observation. 

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