Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

High rates of snowfall late Thursday created dangerous and large storm slabs that you can trigger at any elevation. Don't be lulled into complacency by the nice weather - avoid all slopes steeper than 35 degrees. The avalanche danger will be the greatest first thing in the morning.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2

    High rates of snowfall tend to create instability that takes more than 24 hours to heal. Friday afternoon and evening saw 1-2"+ per hour snowfall rates for multiple hours under light winds. This snow sits on top of 4-5" of snow (redistributed by winds at upper elevations) which fell Wednesday night and sits on top of a strong rain crust. Expect widespread hazard on all slopes greater than 35 degrees where you find 8" or more of snow above the ubiquitous crust. Monitor your slope angle. Use consistent small slope tests to confirm the problem and exercise the most caution early in the day when your danger is greatest and at upper elevations where the winds early in the storm drifted snow to form larger and more dangerous slabs.

     

    (11/24/2020) A quick skin track test as you travel can show you the upper snowpack's slab potential.

Avalanche Discussion

If the sun comes out on Saturday, steep south-facing slopes may also produce small loose wet avalanches. If you observe rollerball activity, change your aspect and reduce your exposure.

Incoming snow bonded well to a refrozen crust following a week of warm, dry weather in early December. The crust should limit your avalanche danger to snow that fell since Thursday. With a good bond between the new snow and the crust, we expect avalanches to be triggered within mid-storm layers that are more challenging to predict. However, the crust provides an excellent bed surface for avalanches to run faster and farther than you expect. If mid-storm layers don't materialize on Thursday, expect loose dry avalanches that you can also trigger on slopes steeper than 35 degrees. These avalanches don't run cohesively, but may still swipe you off your feet and into terrain you might not want to be pushed into.

On Friday, reports from Mt Hood Meadows suggested the presence of wind-affected snow above treeline, a shallow loose dry avalanche problem near treeline, and slightly heavier snow forming a more cohesive slab below treeline.

Régions couvertes