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 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

It is still possible to trigger a large avalanche on an exposed slope where days of snow and winds have built thicker and more dangerous slabs. You are most likely to find a lingering instability in complex terrain below sharp ridge lines, cliff bands, and entrances to gullies. Ease into the terrain, assess stability before committing to steep slopes, and seek out the high-quality snow and safer riding conditions on offer outside of the wind zone.

 

Conditions on Mount St. Helens and Mount Adams are tracking more closely to Mount Hood than the rest of the West South right now. Consider reading the Mount Hood Forecast for a more representative reflection of the current avalanche conditions in these areas.

Problemi valanghivi

  • Wind Slabs

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

    Throughout much of the West South, winds have calmed and loading has subsided. With the decreasing wind speeds, we aren’t likely to be building any fresh wind slabs. The main concern now is older wind slabs that are thicker, more destructive, and less likely to give you any obvious clues of instability. With good visibility, you should be able to visually identify these slabs by looking for signs of wind texture, cornices, and lens-like deposits. What will be more challenging is assessing their stability. To do so, you will need to find a representative and safe location that has all the same characteristics as the slope in question and dig or impact the snow to the depth of any potential instability. As such, the usual uptrack tests, hand pits, and stomping on test slopes may not provide you the full picture.   

    If you are considering steep slopes with signs of wind effect, discuss with your partner the consequences of a slide in case your assessment is wrong. While we expect this problem to be stubborn to trigger on Tuesday, the potential size of any avalanche is worth a pause. Minimize your exposure to the complex terrain features where these slabs could still release, like below cliff bands, at the tops of couloirs, and below ridge lines. There is good powder to be had in sheltered locations, so look for areas free of wind texture where the riding is both better and safer.

    (12/30/2024)

    Signs of wind-transport on a ridge in the Crystal backcountry.  The scalloped features (sastrugi) point to where the wind came from. The cornice is also a red flag. Below sharp ridges like this are where lingering wind slabs could be found on Tuesday.

    Photo: Andy Harrington

Avalanche Discussion

The weather continued to ease through the majority of the West South on Monday. Though Paradise and White Pass still saw some decent snow accumulation over the past 24 hours, most of that fell in the overnight hours from Sunday into Monday. The general trend of dry weather with decreasing wind speeds will continue through Tuesday. While some parts of the zone already saw the sun on Monday, it will be the first time for other locations. If the sun comes on for longer and stronger than anticipated in these areas, give a wider birth to steep slopes as sun on fresh snow can lead to increased reactivity. 

On Tuesday, NWAC forecasters, avalanche professionals, and ski patrollers in the Crystal and White Pass Zones noted great snow quality and no obvious signs of instability. There were clear indications of wind transport along exposed ridge lines, but no reported avalanches, shooting cracks, or other red flags. A slight sun crust was observed on south-facing terrain and one party noted widespread 3-5 mm surface hoar.

Finally, with clearing skies and cool temperatures, snow surfaces may begin to weaken. The next system comes in with relatively low windspeeds and just a bit of precipitation; a good combination for capping and preserving a layer of surface hoar or near-surface facets. If you get out, please let us know what you find within and on top of the snow!

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