Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Warmer temps and sunshine could quickly lead to wet avalanches in the recent snow. With a slick crust underneath, these avalanches could run easily and entrain additional snow. Move off of steep slopes if you are sinking deeply into wet, heavy snow, and be wary of steep, rocky terrain overhead.

Problemi valanghivi

  • Loose Wet

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

    Thursday will likely be a warm day with more sunshine than clouds. You can expect the recent snow to quickly become heavy and wet in the intense April sun and wet loose avalanches to run in steep terrain. These avalanches may start small but could increase in size as they entrain more snow sliding downhill. With a slick crust below the snow, they could also move faster than you may anticipate or trigger larger wet slabs. Rollerballs and pinwheels are the first signs that wet avalanches are becoming more likely. Move off steep terrain if you begin to sink into deep, wet snow or see steep rocks shedding snow in the sun. There may also be lingering glide avalanche potential on rock faces and steep, smooth slopes. So if you see a big frowning glide crack or hanging blocks of snow on rocky ledges, give yourself a wide berth around these unpredictable avalanches. 

    (4/12/2023)

    New rollerballs started with just a little sunshine on 4/11. These are often the precursor to Loose Wet avalanches.

    Photo: Dallas Glass

  • Wind Slabs

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

    You could still find lingering wind slabs in steep terrain at upper elevations. Look for textured surfaces or areas that look "fat" compared to the surrounding landscape to identify wind-loaded features. Using test slopes and hand pits as you travel can indicate the snow's slab potential and the strength of the bond with the old snow surface. Pay close attention to conditions near ridgelines, unsupported slopes, or confined terrain features where you're more likely to trigger one of these small avalanches.

    (4/11/2023)

    A skier-triggered slab in the new storm snow on 4/11. [N 5000']

    Photo: Public Observation

Avalanche Discussion

After several days of rain at Snoqualmie Pass earlier this week, upper elevations picked up roughly 6-9 inches of new snow on Tuesday, with considerably less down low. NWAC forecasters visited the Alpental Valley on Tuesday and Commonwealth Basin on Wednesday. In both locations, they found a poor bond with the underlying surface. Observations from Wednesday indicate that the strength of the bond at this interface is improving, but they could still push loose snow that ran easily on the crust. They also confirmed a widespread natural cycle due to the aforementioned atmospheric river that dropped over 2 inches of precipitation (SWE) on our cold wintertime snowpack. On Wednesday, observers reported multiple new wet avalanches due to daytime warming and direct solar input on the recently fallen snow. The 4/11 crust varied in thickness and stoutness across the landscape.

This is my last forecast for the season, so I hope you have a fun, safe spring. Thanks to the incredible backcountry community for your observations and support of the Northwest Avalanche Center. We'll see you back here in the fall.

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