Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Your risk of triggering a wind slab peaks during the morning hours on steep, lee wind-loaded slopes. These slabs may be most reactive on northerly aspects near the treeline. Once the sun comes out, navigate to cooler, shaded aspects to avoid small natural avalanches that gain steam as they move down the slope.

Problèmes avalancheux

  • Wind Slabs

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

    The north and west sides of Mt. Hood picked up significantly more snow (3-4") than the east side (1") on Tuesday with a snow line around 4000 ft. Strong WNW winds blasted windward aspects and deposited the snow likely onto mid-slope terrain features to the lee side.  We're expecting 2-4" of additional snowfall with decreasing winds blowing the new snow onto similar aspects. Slabs may be covered up by lower-density snow by Wednesday, making the appearance of the snow deceiving. Probing and shovel shear tests on safe test slopes may help you identify firmer over weaker snow layering where wind slabs will be reactive. If denser wind slabs build over weak snow on shady slopes near treeline, they may be touchier and easier to trigger than you expect.  Look for shooting cracks in the new snow and feel for firmer hollow-sounding snow to help you assess the developing hazard. Above treeline, slabs may also be thicker and easier to trigger. Ease into the terrain on Wednesday, steering around steep leeward terrain features. Expect the avalanche danger to peak early in the day.

    Example: Cracking provides evidence you can trigger a wind slab. Photo: Paige Baugher

  • Loose Wet

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

    Expect heightened danger of wet loose avalanches anywhere you find 6" of dry snow with the energy of the strong sunshine impacting the snow surface. Despite cool temperatures on Wednesday, as soon as the sun comes out for any extended period of time, move to more shaded aspects aspects including northerly slopes which may maintain dry snow all day. Rollerballs originating off rocks, trees, and cliffs will lead to small natural avalanches that can entrain sufficient snow to bury you in a terrain trap such as a creek bottom.

    Example: Wet loose avalanches on steep sun-affected slopes.

    Photo: Robert Hahn

Avalanche Discussion

The snow from the 3/8-3/9 storm sits on a variety of surfaces left by the 2/26-3/2 atmospheric river event. Below treeline, snow surfaces were covered in tree debris with a few south and west-facing slopes melted out to bare ground. Between 5500-6500ft, 3-5in of cold recycled powder could be found over a firm crust. Above 6500ft, snow surfaces were a mixed bag with plenty of wind-affected, grabby snow.  During peak precipitation intensity on 2/28, several very large natural avalanches released high on the mountain. In a few cases, these avalanches ran through the rain/snow line around 8000ft and entrained significant wet snow creating very large, river-like debris piles. Check out a few of the largest documented avalanches from the 2/26-3/2 atmospheric river in our avalanche occurrence database: Clark Canyon, Eliot Glacier Headwall, White River Canyon.

High on the slopes of Mt. Hood (above NWAC forecast terrain), several climbers suffered very serious falls that resulted in one fatality and another climber being rescued, but with serious injuries. The cause of the fall is not currently known. Rescuers on Sunday night and Monday encountered strong winds, areas of deep unconsolidated snow, and dry loose avalanches as reported here.

Régions couvertes