Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

With sunny skies and warm temperatures, the weather forecast Sunday looks beautiful, but this could create pockets of unstable snow on steep southerly slopes. Seek out shadier terrain if you see new rollerballs or find the wet heavy snow as you travel.

Problèmes avalancheux

  • Loose Wet

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

    It’s easy to write-off the effect of the sun when the calendar says November and the sun is low in the sky. But, when we combine sunshine with warm temperatures like we’re expecting Sunday, you can get loose wet avalanches despite the date on the calendar. On Friday, similar weather produced natural loose wet avalanches on very steep slopes near Paradise on Mt Rainier. Early signs of unstable snow include new rollerballs or thick heavy snow sticking to your feet or machine. If you see this, head for shadier locations. Cool winds and slightly lower freezing levels allowed upper elevations to escape most of the recent warm-ups. As a result, alpine locations could be most affected by Sunday’s weather. At lower elevations, most southerly slopes underwent a melt-cycle Friday, which should help minimize danger.

    (11/27/2020) Pinwheels at Mt. Rainier after rising freezing levels and the sun came out a few days after a storm. [S aspect 5400']

Avalanche Discussion

The biggest question in the forecast for Sunday is cloud cover. We expect clouds associated with an approaching storm to stay to the west of the mountains for most or all of the day. However, if they arrive early, that could curtail the avalanche hazard. Additionally, you could find yourself reaching for a warmer coat at the trailheads near White Pass or in the deep valley bottoms Sunday morning. Don’t let these temperature inversions fool you. Expect much warmer weather was you ascend to higher elevations. 

The past five to six days provided a series of precipitation and wind events that drove slab avalanche danger at mid and upper elevations. As we get further and further from these loading events, it becomes harder and harder to find and trigger a lingering wind slab. However, if you use the nice weather Sunday to travel up into the alpine don’t rule out an isolated slab in very steep leeward terrain.

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