Boletín de aludes

Mt Hood

Northwest Avalanche Center
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Peligro de aludes

Sat
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Sunshine will break down surface crusts to initiate potentially large avalanches on steep slopes exposed to sunshine. At upper elevations, large and sensitive cornices deserve extra space as you travel along ridgelines or on the slopes below where large wind drifts remain reactive. Keep your terrain selection simple as you navigate a complex set of avalanche problems.

Problemas de aludes

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Mt. Hood picked up 15-20" of snow since Monday. Rainfall formed a 4/20 crust down 6-8" near treeline. Additional crusts formed during a period of intense sunshine Thursday afternoon, which may have several inches of additional low-density snow on top of it by Friday morning. There's plenty of dry snow that remains susceptible to wet loose avalanches. You'll need to assess the amount of snow above a supportable crust because this is the depth of snow in play as the sun begins impacting the snowpack on Friday. At this time we expect that morning partial sunshine will allow for a marked increase in wet loose activity on all aspects, but that before this activity becomes widespread, winds and afternoon clouds/precipitation will limit wet loose activity before it becomes widespread. In this case, limit your exposure to steep slopes warming in the sunshine. However, if the sun remains strong or the winds light and you notice supportable crusts breaking down, dial back your terrain selection further and assume any slope greater than 35 degrees could produce a large avalanche.

    Example: Natural wet loose avalanche.

    Photo: Robert Hahn

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Moderate SW winds continued to build slabs through the day on Thursday, but reduced snowfall, moderating temperatures, and sunshine Thursday afternoon and Friday morning have begun a gradual stabilization trend that likely neutralized slabs on aspects receiving strong direct sunshine Thursday afternoon. Wind slabs remain reactive on other aspects, particularly on N and E aspects. Some will be large enough to bury you. Large cornices have overbuilt, remain fragile, and threaten wind-loaded slopes below them.  Use recently formed cornices along ridgelines to evaluate loading patterns and make sure you're not in the runout of cornices that threaten you in their own right or may trigger a wind slab on a 35-degree or steeper slope below. These cornices also deserve a wide berth as you travel along ridgelines. Shooting cracks, recent avalanche crowns, and large variations in snow depth all indicate that slabs should be present on wind-loaded slopes nearby.

    (4/21/2022)

    Skier triggered cornice fall which could easily trigger a wind slab on the slope below.

    Photo: Andrew Kiefer

Avalanche Discussion

NWAC forecast Andrew Kiefer was in the Pea Gravel Ridge area adjacent to Mt. Hood Meadows on Thursday. He found reactive cornices, fresh natural and human-triggered size 1.5 wind slabs, and even some slab formation below treeline. Warm temperatures and afternoon sunshine started a rollerball cycle as he exited the field in the early afternoon and should form a crust as temperatures cool Thursday night. You can read his full observation here.

Winter-like conditions remain on Mt. Hood thanks to a cold and snowy April, but don't forget the power of the April sun. Mt. Hood has picked up 80-100" of snow since April 8th, with 1.5-2 ft falling since Monday.

NWAC is aware of a possible avalanche fatality at Mt. Hood Meadows on 4/5. We are actively working with local authorities to gather more information about the incident. This incident involved a solo snowboarder and a multi-day SAR effort. You can read our initial statement here.

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