Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

Wind slabs will be more reactive in areas with recently formed drifts near ridgelines and in avalanche start zones. Given limited recent observations near and above treeline, it's a good idea to evaluate the upper snowpack before committing to larger open slopes. It's deep out there in sheltered areas, so ride with a partner and keep them in sight.

Problèmes avalancheux

  • Wind Slabs

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

    Winds continued to drift some snow near ridgelines on Saturday and that trend should continue Saturday night. Slabs will continue to build and will remain reactive anywhere with signs of wind-affected snow. Wind-stiffened snow, bulging pillows, textured snow, shooting cracks, or difficult trail-breaking conditions are all indicators that you may be moving into wind-affected terrain where you can trigger an avalanche. The most likely places to trigger wind slabs will be steep slopes below ridges, convex rolls, and the base of cliffs. You will likely need to steer around these wind slabs in steep open terrain near treeline, and the potential remains more elevated danger in heavily wind-exposed terrain above treeline. Feel for stiff over soft snow layering and use inconsequential test slopes to identify and avoid areas of unstable wind-drifted snow. Navigate away from lee slopes steeper than 35 degrees, instead choosing sheltered slopes and lower-angle terrain will offer high quality and safer riding conditions.

    Example: Wind loading in both directions forming cornices with potentially reactive slabs on the slopes below.

    Photo: Sam Siemens-Luthy

  • Loose Wet

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

    With all the low-density recent snow, it won't take much sunshine to release a loose avalanche (wet or dry). Rollerballs serve as a first warning sign to seek shaded aspects. If you enter terrain approaching 40 degrees, expect sluffs to run far and fast within dry snow.

     

    Example: Precursors to wet avalanches, rollerballs and pinwheels remind you to seek colder, shaded aspects.

    Photo: Ron Martin

Avalanche Discussion

NWAC forecaster Joe Dellaporta was in the Elk Mountain area. He found reactive pockets of wind-drifted snow that we easily triggered on test slopes. Slabs were generally shallow, 6-12 inches deep in an area that behaved like near treeline terrain, running on the 3/2 interface of decomposing snow grains. Sharp, fresh cornices along the ridgeline kept them off of the steeper slopes below. They found a firmer crust-like layer around 6" down and continued to find some reactivity at the 3/2 interface (but did not find evidence of buried surface hoar). Around 31" of snow now sits above the 2/21 freezing rain crust.

Stormy weather continues to limit observations at upper elevations, leaving us with more uncertainty following an extreme wind event late last week. Good riding conditions can still be found in sheltered locations.

As the snow keeps piling up, keep SIS safety in mind: keep your partners in close sight and give tree-wells a wider buffer than normal.

Régions couvertes