Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 7 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Avoid steep slopes that are warming or showing signs of wet snow instability, and limit time beneath overhead hazards like cornices or glide cracks. Watch for rollerballs, small wet avalanches, or sloppy snow surfaces. Avalanche danger will trend higher at upper elevations as temperatures rise above freezing.

Problemi valanghivi

  • Loose Wet

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

    Continued warmth and periods of light rain will keep wet avalanche concerns in play into the weekend. Mid-elevation terrain has already seen a cycle of natural wet avalanches in some areas. The greatest risk may shift to upper elevations as snow levels rise and warming reaches terrain that has received significant snowfall over the past three days. Be prepared for a sharp uptick in wet avalanche activity if the sun breaks through the cloud cover.

    Wet avalanches are most likely on slopes below steep rocky headwalls and cliffs as temperatures rise. Cornices and glide avalanches remain a low-likelihood concern during sustained warming. While the likelihood of natural avalanches is decreasing at mid-elevations, expect to get some wet snow or big pinwheels moving downhill with you if choosing to descend very steep slopes.

    (2/7/2024)

    Example of wet loose avalanches below extreme terrain.

    Photo: Jonathan Spitzer

  • Wind Slabs

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

    Winds were ripping on Friday, with gusts into the 50s at 5,000 feet, and upper-elevation areas picked up another 6-12 inches or more of relatively dry snow. Wind slabs are all but guaranteed on leeward slopes in alpine terrain. You may also find wind slabs at mid elevations farther east in the forecast zone, where temperatures remained colder.

    Recent wind slabs are likely thick and stubborn to trigger, but don’t assume they are stable. Use lower-angled terrain to avoid steep, unsupported features loaded with wind-drifted snow. Cornices and scoured snow surfaces are good clues for identifying which slopes have been the most heavily wind-loaded.

    As temperatures warm, natural slab avalanches are possible where snow sheds off cliffy or extreme terrain and triggers a slab on the slope below. Pay attention to changing conditions.

    (1/29/2023)

    Wind-affected snow surfaces can help identify areas of wind slab.

    Photo: Lee Lazzara

Avalanche Discussion

The mountains picked up another 0.5 to 2.0 inches of precipitation over the past 24 hours. Warm temperatures limited snow accumulation at mid-elevations, with most weather stations reporting minimal snowfall. The exception was stations above 5,000 feet or farther east in the zone, where colder temperatures allowed up to 6 inches of new snow to accumulate. On-the-ground observations were limited due to wet weather, very strong winds, and marginal travel conditions.

The remaining question is whether faceting along the old crust could contribute to larger slab avalanches. Faceting has been observed on shaded aspects, but distribution has been inconsistent. Rain at low and mid elevations will likely dampen or destroy any remaining facets, while colder upper-elevation terrain and areas farther east in the zone are where they may be best preserved.

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