Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

You can trigger a large wind slab at upper elevations where you should check for punchy snow layers before committing to larger terrain features. Point releases will entrain recent snow to form dry avalanhces on very steep, shaded aspects or wet where sunshine destabilizes previously dry snow. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    You can trigger a large wind slab at upper elevations with shallower slab potential near treeline. Strong WNW winds transported significant snow early in the 3/8-3/9 storm. The wind slab problem may be inconsistent on Thursday. Mt. Hood Pro Patrol only found small 2-4" dry loose avalanches while a large crown was visible high in White River Canyon. Potentially reactive slabs lurk under less wind-affected snow. 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. Continue to ascend to upper elevations with caution, using smaller test slopes before committing to steep or unsupported terrain features that show any signs of wind loading. 

    (3/9/2022)

    Large wind slab avalanche, likely several days old, with crown visible around 8600 - 8800 ft. 

    Photo: Ron Martin

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    With cold temperatures and cloud cover, snow surfaces stayed dry and Mt. Hood Meadows reported only dry loose avalanches. Thursday will be a battle between strong March radiation and gradually increasing clouds. We expect steep slopes facing direct sunshine to destabilize as the snow warms. Rollerballs originating from snow melting off rocks and trees foretell wet loose avalanches that should increase in size in areas that received more snow atop the 3/7 interface. Reduce your exposure to steep slopes with melting snow surfaces once you feel the impact of the sun's energy. On colder shaded aspects, dry loose avalanches should continue to run efficiently on melt-freeze crusts or a weak, sugary interface.  You can trigger these in very steep or extreme terrain. Regardless of which type of loose avalanche you're dealing with, the consequences will be amplified by terrain traps including cliffs and gullies on the slopes below you.

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

    Photo: Robert Hahn

Avalanche Discussion

A storm system 3/8 - 3/9 brought 4-8" of fresh snow with higher snow totals on the west and north sides of the mountain. Strong WNW winds redeposited the new snow early in the storm.  This snow sits on a variety of surfaces left by the 2/26-3/2 atmospheric river event which deposited tree debris on the new/old snow interface and also left a few south and west-facing slopes melted out to the ground. Between 5500-6500ft, wind slabs or loose snow may sit on 3-5in of cold recycled powder. Slabs sitting on this interface may propagate farther than you expect, making them more difficult to manage. Above 6500ft, the storm snow sits on previously wind-affected surfaces. Several very large natural avalanches released high on the mountain during the atmospheric river. 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 in the Leuthold Couloir suffered 200 ft falls on Sunday that resulted in one fatality and another was rescued with serious injuries.  Another party in the Leuthold couloir on Sunday reported dry loose avalanche activity while rescuers on Sunday night and Monday encountered strong winds and areas of deep unconsolidated snow. The cause of the fall is not currently known. 

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