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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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You can trigger avalanches where new snow and wind build fresh slabs at upper elevations. As the sun warms steep, sunny slopes, you may encounter small wet avalanches.  Triggering large avalanches on older buried weak layers is unlikely, though not impossible. Put extra space between your group and large, consequential pieces of terrain where avalanches could start.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Avalanches will be easy to trigger at the highest elevations. While winds will be dropping off on Monday, observers reported fresh slabs and blowing snow on Sunday. Watch for blowing snow and wind features to point towards the slopes prone to these avalanches. To avoid these avalanches, you can steer around drifted pillows, stick to scoured or wind-sheltered terrain, or travel on slopes less than 35 degrees. 

    (1/22/2023)

    A very shallow wind slab avalanche ran on the MLK crust. Henry Creek clearcut.

    Photo: Joe Dellaporta

  • Loose Wet

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

    The sun will warm steep, southerly slopes, where you may see some small loose avalanches. Southeast aspects will get warm and weak first and southwest aspects will be more prone to avalanches in the afternoon. Watch for moist snow surfaces and rollerballs as indicators before an avalanche occurs. If you see these or other recent wet avalanches, move to lower-angled or more shaded terrain. Don't linger under steep rocky terrain, as natural avalanches could come down from above.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1.5–2

    The safest option is to stick to slopes under 35 degrees in areas suspected for the weak layer. Put a large buffer of terrain between where you travel and areas where avalanches could start. You can stick to smaller features and avoid traveling through start zones. The January 4th buried surface hoar can be found about 1-2 feet below the surface of the snow. Use snowpits and propagating snowpack tests in safe terrain to look for the stripe of feathery snow grains. While the layer may only exist in isolated areas, the consequences of a slide could be serious.

    On the 19th, skiers triggered a large avalanche 1-2 feet deep on Jim Hill. While the January 4th surface hoar has been found in a few other locations, we don't have a lot of other information on it in this zone. The most likely areas to trigger an avalanche on the layer would be between about 5,800-6,500ft in wind-sheltered terrain. In the neighboring East Central zone, there have been multiple observations including large natural avalanches running on this layer.

    (1/19/2023)

    Large avalanche on a layer of buried surface hoar. NE at 6,200ft on Jim Hill. The crown was 1-2ft deep.

    Photo: Ryan Minton

Avalanche Discussion

On Sunday, observers triggered small wind slab avalanches in newly formed drifts. Stevens Pass Patrol triggered a slide (D1.5) in the notorious wind funnel of Gemini Pass. An observer in the Henry Creek clear-cuts was able to trigger very shallow slab avalanches that ran on the MLK crust in wind-exposed terrain below treeline. 

Régions couvertes