Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

Very dangerous avalanche conditions will develop at mid and upper elevations as rain impacts a cold dry snowpack. This won’t be the day to try and thread the needle. Instead, give avalanche terrain a wide berth and stay off of and out from under steep open slopes.

Problemi valanghivi

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1.5–2.5

    Significant rain will reach high into the mountains Saturday and likely result in large natural avalanches. While these slides may take many forms and could fail on any number of weak layers, the message remains the same. This won’t be an easy hazard to manage. Avoid traveling in areas where avalanches start, run, and stop at mid and upper elevations. As water percolates deeper into the snowpack, slides could fail on older weak layers creating larger avalanches that travel further into their runouts.

    At lower elevations, rain from Friday will likely help to soften this abrupt weather transition and should result in slightly lower avalanche danger.

    Above the rain-line heavy wet snow and strong winds will continue to overload the snowpack. Even though it’s snowing, you will likely still find very dangerous conditions with natural avalanches.

    (12/23/2022)

    This natural wet slab avalanche below treeline at Mt Rainier, may hint at what's to come in the West South zone Saturday. NW 3800ft

    Photo: NPS Rainier Rangers

Avalanche Discussion

While there’s a lot of complexity and uncertainty with this forecast, the trends and fundamentals remain the same. Different locations across the zone may reach the tipping point at different times. However, all areas seem to be barreling towards very dangerous conditions as temperatures warm and rain reaches higher elevations. In some ways this storm is simple. We have a very cold, dry, and layered snowpack that will likely not handle the change to much warmer and rainy weather very well. This will be the first rain the snowpack has seen since mid-November. As a result, you may see all types of avalanches Saturday: loose wet, wet slab, storm slab, wind slab, and even persistent slab. With so many potential weak layers that could fail, it's hard to say exactly what it will take to cause a large widespread natural avalanche cycle, but the conditions seem favorable.

On Friday, NPS rangers at Mt Rainier reported one natural wet slab and numerous loose wet slides well below treeline (3800ft). This seems like an indicator of what’s to come as temperatures continue to warm and more rain falls.

While observations were limited, Crystal Mt Ski Patrol reported rain to 6100ft that resulted in a few small loose wet avalanches. White Pass Ski Patrol also observed rain and mixed precipitation at 6000ft, with freezing rain at lower elevations. This ice crust could temporarily limit avalanche issues in this terrain until it melts.

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