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

You’ll need to manage overlapping avalanche problems as this small storm comes to an end and the sun returns Tuesday. You’re most likely to trigger avalanches on wind-loaded slopes or in terrain receiving direct sunshine.

Problemi valanghivi

  • Loose Wet

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

    As the sun comes out Tuesday afternoon, expect the new snow to start to slide downhill. Rollerballs and snow shedding from rocks/trees will be your first warning sign. Once you see these clues, loose wet avalanches won’t be far behind. What could make this round of loose wet avalanches different is the presence of a crust underneath the new snow. This may allow slides to run quickly or travel far downhill. Fortunately, the modest new snow totals should help limit the size of any avalanche. Just don’t let one push you over a cliff or into a creek. 

    At lower elevations, there shouldn’t be enough new snow to present a hazard. Instead, you may see a few piles of rollerballs.

    (3/17/2023)

    Recent rollerball and Wet Loose avalanches on a steep sunny slope. Note how they originate at a point near rocks and trees.

    Photo: Rachel Gronvold

  • Wind Slabs

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

    You’re most likely to encounter a significant wind slab on the volcanoes, where more snow fell Monday. In these locations, look for textured snow, cornices, and drifts to point toward wind-loaded features. You could trigger a pillow-like slab below cornices, in the tops of chutes, or along the base of cliffs. In general, these wind slabs should be easy to spot and simply go around. 

    In areas that received less snow, you may encounter pockets of wind-loaded snow. These slabs should be very small, shallow, and relatively isolated. They shouldn’t produce much risk unless you’re traveling in very high consequence terrain.

    (2/24/2023) Wind clues like these can help you anticipate wind loaded aspects. Photo: Dallas Glass

Avalanche Discussion

The West South zone received a nice little shot of snow on Monday. Weather stations around the area indicated sites received 2-8 in (5-20cm) of new snow during this little storm. The greatest totals were recorded on Mt St Helens and Mt Rainier. Another inch or two of snow Monday night won’t do much to affect the avalanche danger. The biggest factor on Tuesday will be the sky and warming temperatures. Look for the greatest hazard in the afternoon once the skies start to clear. 

In addition to the hazards in the recent snow, there are a few other concerns about cornice, glide, and very isolated deeper avalanches. The reality is, this is the first spring warm-up or cold dry, and layered winter snowpack has seen. Predicting how it may react to this big change is quite challenging and brings a bit of uncertainty. While these much larger slides should be very rare on Tuesday, they are not impossible. You can reduce your risk to them, by limiting the time you spend under looming cornices, crevasse-like glide cracks, and sunny complex terrain. 

This weekend’s warm weather resulted in numerous loose wet avalanches around the zone. While observations were few and far between, you may find piles of older debris from this avalanche cycle. Even though the snow surface became wet at lower elevations and on southerly aspects, cold soft snow may still be found in shaded areas higher in the terrain.

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