Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

An atmospheric river is set to impact the West South zone on Sunday, resulting in very dangerous avalanche conditions. Expect wet avalanches large enough to bury and kill you to occur on most steep slopes. It likely won’t be a very pleasant day outside, so better to stay out of the mountains until the rain has stopped.

Avalanche problems

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2

    Wet avalanches will be prevalent throughout the mountains on Sunday, including slabs, loose, glide, and cornice collapses. You will likely see snow falling off rocks and ledges that are harder to put a name to. We’ll just call them "spring shedding-type" slides. The problems could vary from slope to slope or at different points during this rain event, sometimes overlapping. Any avalanche has the potential to grow large as it gouges down into older layers or entrains snow as it descends. Some could run far distances down into the trees. Sunday will not be a good day to hang out in terrain where avalanches can start, run, or stop.

    Although some drier snow may fall at upper elevations to start this event, rising freezing levels mean that any new snow problems will eventually transition to wet snow problems. Don’t overthink it, Sunday is not the day to play in the mountains.

    (12/23/2022)

    Example: Natural wet slab avalanche below treeline at Mt Rainier that occurred during an atmospheric river event earlier this season.

    Photo: NPS Rainier Rangers

Avalanche Discussion

Depending on your location in the West South, the incoming atmospheric river may play out a little bit differently. Areas in the southeastern part of the zone may escape the bulk of the precip but don’t hang your hat on it. In areas such as the volcanoes and Crystal Mountain, significant rain is forecasted to reach ridgecrest as the day progresses. 

With a poor overnight refreeze expected, rising snow levels, and increasing precipitation rates, you could say that the hazard will escalate throughout the day. With events like this, sometimes it is best to not overthink it and try to thread the needle. No matter how you shake it, Sunday will be a nasty day in the mountains with very dangerous avalanche conditions expected. Stay out of the hills until this event has wrapped up in a few days.

Although the snow surface may already be wet from recent rain and sunny springtime weather, the moist snow only extends so deep. Below the wetting front, a layered cold dry snowpack exists with multiple interfaces capable of failing if water is able to percolate to their depth. Not to mention that there are plenty of precariously hanging cornices or blocks of snow on rocky ledges that need to come down as we transition from winter to spring.

Regions covered