Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Be leery of wind-affected snow, especially if the slope below you ends in a cliff, tree fence, or other terrain trap. Look closely for pillow-like slabs you may want to avoid. Given the recent wind direction, you could find wind-loaded pockets on some strange aspects.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Keep your eyes open for areas of wind-affected snow near ridges, below cornices, and in rocky complex terrain where you’re most likely to encounter fresh soft wind slabs. These pillow-like pockets should be easy to spot and avoid. Blowing snow, sharp wind lips, and drifts should help you figure out where to look. Given the recent E-S winds, you may find wind-loaded slopes on some unusual aspects. While most of these slabs should remain small, they could travel far downhill and carry you for a long unwanted ride. 

    A few larger (D2) hard slabs may still linger from this weekend’s stronger SE wind event. If you find very firm or hollow sounding snow, steer around it. Hard slabs are notoriously difficult to assess and can break above you with little warning. 

    (3/6/2023) Reverse loading results in wind slabs in some unexpected places. Photo: Dallas Glass

Avalanche Discussion

Snow showers should bring a few additional inches of snow to the West South zone by Tuesday afternoon. Even if you find yourself under a locally intense shower, it shouldn’t do much to affect the avalanche danger. Instead, it will only keep refreshing the very soft and fluffy snow surface.

Over the past 9 days, 2.5-4 ft of snow has fallen around the zone (with more at Mt St Helens). These storms occurred with cold temperatures and resulted in generally right-side-up snow conditions. Not surprisingly, avalanche activity has been limited to a few small natural and human-triggered wind slabs and loose dry avalanches. 

On Monday, an NWAC forecaster in the Crystal backcountry found ample evidence of the recent E-S wind events that loaded more westerly aspects. He also intentionally triggered 4 shallow (4-8in) soft wind slabs. While these wind-loaded pockets were small, they easily entrained snow and traveled several hundred feet down the slope. Outside of wind-affected terrain, deep soft powder remained. 

The sky continues to be a big question each day. We expect periods of sunshine, but increasing clouds and a thin crust on steep southerly aspects should help limit any loose wet activity. However, if you experience prolonged periods of warm sunny weather, expect the snow to shed for rocks and trees. This could trigger loose slides on the slopes below. Pay attention if you see new rollerballs or teardrop piles of debris. Avalanches could follow on similar terrain.

Regioni coperte