Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

You main avalanche concern is wet avalanches on steep, sunny slopes. If you're in wet, heavy snow and see rollerballs or wet avalanches running down, stick to lower angle terrain or cooler aspects. Expect breakable crusts at mid and lower elevations on shady aspects. 

Problèmes avalancheux

  • Loose Wet

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

    Warm wet weather on Sunday led to wet loose avalanches on all aspects at lower and mid elevations. Sunday night skies cleared, and wet avalanche activity was limited to sunny slopes on Monday. Rollerballs and predominantly small, shallow avalanches resulted. You can expect similar conditions on Tuesday. Lower elevations have already been so impacted by rain and wet snow that you can expect less activity down there. 

    A distinct difference on Tuesday is that incoming midday clouds will likely have an effect on wet loose activity, as it could lead to one of two things happening: 1) wet activity could slow with clouds inhibiting the sun's intensity, or 2) cloud cover may cause "greenhousing", where snow on all aspects moistens and wet loose avalanche activity occurs everywhere.  

    Focus on snow surfaces around where you travel- Is the surface moist? Are you causing rollerballs or small shallow avalanches, or do you see them on steep slopes near you? If you say yes to any of these questions, it's time to start planning an exit strategy. Transition to cooler aspects or stay off and away from slopes steeper than 35°.

    (12/10/2024)

    Example photo: Rollerballs often preceed wet loose avalanches.

    Photo: Irene Henninger

Avalanche Discussion

Snow surfaces vary quite a bit depending on where you travel. A breakable crust exists at most low and mid elevations. Sunny slopes will soften quickly and become moist. Prepare for challenging snow conditions during your outing. 

There's a small chance that you could trigger an avalanche in a wind slab pocket at upper elevations. There also may be a chance that isolated pockets of preserved surface hoar exist at the New Year's interface about 2ft deep at upper elevations. In most areas these appear to have broken down and are no longer reactive, but information at upper elevations is very limited.  

South-facing aspects that became sun-baked on Monday may not have as much avalanche activity as the previous day. Clear overnight skies will hopefully lock all surfaces up for Tuesday morning. Temperatures are supposed to get warmer during the day and with incoming cloud cover we're not sure exactly how the radiation balance will pan out and how much wet avalanche activity we'll see. 

About 6" of snow fell at mid and upper elevations Friday afternoon into Saturday, and then another 6-12" or so fell Saturday into Sunday. Storm totals varied widely throughout the zone. These storms were relatively warm, with wet loose avalanches and shallow natural storm slabs resulting. Most of the storm instabilities that failed during and just after the storm have settled out. 

Régions couvertes