Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Recent rain and sustained warmth are keeping the threat of large wet avalanches and cornice falls alive. While not every upper and mid-elevation slope is a problem, there’s no reliable way to spot the ones that are. If you’re not steering clear entirely, limit your time on and beneath steep slopes, avalanche paths, and sagging cornices.

Problemi valanghivi

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    The full buffet of wet avalanches is on offer Thursday: wet slab, glide, wet loose, and cornice failures. Though the temperatures will be cooler than the past few days, that won't have an effect on the freewater deeper in the snowpack driving the ongoing avalanche danger. While wet loose avalanches could be triggered by a human on a steep slope or fail naturally, our biggest concern is that a destructive wet or glide slab avalanche could release on its own, without warning. These slides are most likely to originate at the upper and middle-elevations, but if a big one lets go, it could run for thousands of feet, breaking trees as it charges down into the lower-elevations. In addition, cornices are sagging in the heat and if they fail, they could trigger slab or loose avalanches below. The chances of a large avalanche may have decreased, but the snowpack is full of free water and wet slab activity, natural and explosive-triggered is ongoing.

    Here's the thing, the one certainty with wet and glide avalanche prediction is uncertainty. It's quite possible that you won't see large avalanches on steep slopes tomorrow, but we also wouldn't be surprised to see a very large and destructive avalanche release naturally. How to manage uncertainty like that is a personal decision, but recognize that this problem is still out there and if you are in the wrong place at the wrong time, it would likely be unsurvivable. The safest bet is still avoidance, closely followed by minimizing your exposure and traveling quickly and one at a time if you have to cross a path.

    (3/26/2025)

    A very large wet slab avalanche was explosively triggered by Crystal Pro Patrol on Wednesday afternoon. This slide was 300-400ft wide, broke 4 to 6ft deep, and appears to have run on the old 1/10 crust. While this may be an outlier result, it does nothing to inspire confidence in the state of the snowpack. Until we get a refreeze, there will a be chance of a large and unpredictable wet slab avalanche.

    N, 6800ft. WS-AE-D3-O

    Photo: Josh Lipkowitz

Avalanche Discussion

It was another unseasonably warm day in the West South, with temperatures reaching well into the 50's. NWAC Forecasters near Crystal Mountain noted sagging, though slightly trimmed back cornices, while continuing to document the recent cycle, adding more slides to the large, very large, and historic avalanches observed in the Goat Rocks and on Mount Rainier. Best we can tell, these slides occurred during, or immediately after the 1-2.25" of rainfall on 3/23-3/24. Though that may have been the crescendo of activity, free water in the snowpack is still percolating to parts unknown, and we don't trust it. The 5" of snow settlement in the past 24 hours is a clear indication that the snowpack is still adjusting and changing. While lower-elevations appear to be well-drained and unlikely to produce a large avalanche, deeper interfaces on certain slopes may only just be seeing liquid water. To that point, on Wednesday, there were two highly notable avalanche occurrences. NWAC Forecasters at Mt. Hood observed a fresh large wet slab avalanche that released naturally. Meanwhile, Crystal Pro Patrol was able to trigger a very large wet slab with explosives that broke 4-6ft deep and propagated 300 to 400ft wide. These slides serve as important reminders of the unpredictability and ongoing danger in the backcountry right now. Ultimately, we need a solid refreeze, and we won't get one yet. Thunderstorms Wednesday night aren't likely to significantly alter the landscape on Thursday, but they won't help things either. We may eek out a few inches of snow at the higher elevations, but that also isn't likely to add much to the avalanche picture. 

What does this mean for mountain travel? Well, for one, travel conditions are sloppy, sticky, and arduous, at all elevations. As far as the avalanches are concerned, we can't rule out a large and destructive slide, and that should be the thing shaping your decision-making. In addition, another round of afternoon thunderstorms could roll in Thursday, so make a plan to get out of the mountains quickly if need be. The general weather pattern for the next few weeks looks decent and there is plenty of snow in the mountains. The transition season can be tough, but stay patient; both avalanche and travel conditions should improve soon. 

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