Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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

The storm party will keep raging in the West South zone, particularly on the volcanoes where very dangerous avalanche conditions are expected. Regardless of your location, there is plenty of new snow that needs time to settle and heal. Approach slopes over 35 degrees with caution where you're more likely to trigger an avalanche large enough to bury and kill you.

Problemi valanghivi

  • Storm Slabs

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

    Several rounds of precipitation, strong to extreme winds, and fluctuating freezing levels have created several potential weak points in the storm snow. The depth of potential slabs will vary based on location, elevation, and exposure to wind, but the larger end of the spectrum could be several feet deep. You'll need to dig down with your hand or shovel to look for potential failure points, often indicated by heavy over softer snow (upside-down snowpack). Use small test slopes or uptrack tests as you travel to get information about how the snow reacts to your weight, but don't make them your only assessment tool. Potential weak layers may be too deep for those tests to be reliable.. Shooting cracks or recent avalanches are red flag signs of instability that should not be ignored. You should avoid slopes over 35 degrees where slab avalanches are more likely. On the volcanoes, you should avoid all terrain where avalanches can start, run, or stop.

    (12/26/2024)

    A large (D2) slab avalanche that occurred naturally in steep rocky terrain at Crystal Mounain on 12/26.

    Photo: Crystal Mountain Pro Patrol

Avalanche Discussion

Friday will be a relative lull in this week's storm parade, but not so much for the volcanoes of the West South zone. In these locations, expect another foot+ of snow to stack up by the end of the day, accompanied by moderate winds. That should be enough continued loading on the heels of Thursday's storm to maintain high avalanche danger for Mount St. Helens, Mt. Adams, and Mount Rainier. You should avoid all terrain where avalanches can start, run, or stop in these locations.

Speaking of Thursday's storm, it was a doozy. Most NWAC weather stations recorded 1.5-2 feet of new snow, and we are the first zone in the NWAC network to reach 100" this season. Both Chinook Pass and Paradise exceeded the century mark (take that, Baker!) Winds were strong to extreme in many locations, with gusts as high as 90 mph recorded. White Pass Pro Patrol reported sensitive storm slabs during their morning mitigation work, with some propagating as widely as 100 feet. NPS road crews reported natural avalanche activity as they worked to maintain the Paradise road. Backcountry observations were limited, but one avalanche professional in the Crystal Mountain area noted significant wind transport, poor visibility, and limited avalanche activity. Over in the resort, Crystal patrol reported triggering 15-20" slabs throughout their mitigation efforts and similar natural activity in favored locations.

The threat of natural avalanches will be lessened on Friday near the crest, but that doesn't mean it is non-existent. They will be more likely during or shortly following periods of heavy precipitation rates or strong winds. Steep slopes are now be primed for human-triggered slides, so work into terrain slowly and make good assessments before committing to a slope. Continued snowfall and winds will only expand the number of potential weak points but all avalanche activity should be confined to the snow above the easily identifiable Solstice Crust.

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