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
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The amount of sunshine on Friday will determine how widespread the Wet Loose avalanche problem will be. If you find yourself in full sunshine and notice recent avalanches, dangerous avalanche conditions may have developed and you should head toward shaded slopes. At upper elevations, recent storm snow may still produce slab avalanches on specific terrain features.

Problemi valanghivi

  • Loose Wet

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

    Sun breaks combined with springtime temperatures could have enough influence to drive Wet Loose avalanches on Friday. Take a look at the snow surface where you are traveling to determine if it has become warm and sticky. If so, the recent storm snow could destabilize and produce some natural avalanches or you may be able to push snow downhill, creating a Wet Loose. These avalanches will be more likely depending on the amount of sunshine that can make its way through the clouds and tend to develop on slopes that see direct sunshine. Wet Loose avalanches often start at a point and can entrain snow, fan-out, or even trigger slabs as they descend downhill. Besides taking note of the snow surface, you can look for precursors to Wet Loose avalanches such as pinwheels and rollerballs as an indication to head toward shaded slopes to avoid this hazard.

    (3/23/2021) Natural loose wet avalanches occurred on Tuesday when periods of sunshine caused the snow surface to become wet and unstable.

  • Storm Slabs

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

    Continue to keep an eye out for slab potential as you ascend in elevation to where the snow is deeper and drier. With around 10 inches of new snow at upper elevations, you should use test slopes, uptrack tests, or hand pits to help you determine how the recent snow has bonded to the old snow surface. Convex rollovers, terrain features over 35 degrees, or wind-loaded terrain including confined gullies or the base of cliffs, are the more likely locations for you to trigger one of these slabs on Friday. If you find a poor bond during your testing or notice cracking in the recent snow as you travel, look to avoid these features.

    (3/21/2021) Uptrack tests like this can be performed by any mode of travel. They can highlight weaknesses within the recent storm snow.

Avalanche Discussion

Wednesday night’s storm produced around 10” of new snow for the pass at upper elevations (3/24 interface). While the lower elevations received considerably less, there was fresh snow at most trailheads on Thursday morning. There now sits around 25” of snow above the 3/18 interface and both the 3/18 and 3/24 are easily identified on slopes that see direct sunshine. On slopes with a more northerly tilt, you should be able to still find them, but they could be a bit more subtle. We believe that all avalanche activity should occur above the 3/18 interface, with most focused above the 3/24. However, slopes may act differently depending on the aspect and surface the recent snow fell on, so be sure to choose representative testing locations. 

On Thursday, Alpental Pro Patrol reported slabs as deep as 10” running at the 3/24 interface during their control work measures and also mentioned that fresh cornices have developed, with a few failing throughout the morning. Mostly cloudy skies kept a widespread natural Wet Loose cycle at bay, but the new snow didn’t fully escape the sunshine. Sun breaks were enough for snow surfaces to get warm and sticky, resulting in some rollerballs, treesbombs, and isolated Wet Loose avalanches on slopes that see direct sunshine. Look for similar conditions on Friday but be prepared to change your travel plans if the cloud forecast doesn’t verify and you find yourself in full sunshine. This could lead to a more widespread and dangerous Wet Loose avalanche cycle.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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