Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

A multi-day storm should culminate in dangerous avalanche conditions by Saturday morning at Snoqualmie Pass. Look for cracking of the snow surface or a poor bond within or at the base of the storm snow as an indication to avoid slopes over 35 degrees. As the day unfolds, you may have to switch your mindset to focus on wind-loaded features or potentially sun-exposed slopes.

Problemi valanghivi

  • Storm Slabs

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

    Snowfall is forecasted to continue throughout Friday night and into Saturday morning at Snoqualmie Pass. With accumulations possibly being enhanced by a convergence zone, storm totals are expected to reach depths where you should be thinking about slab avalanches on all steep slopes. Of course, in wind-loaded areas slabs will be thicker and potentially more reactive. This is especially true on specific features such as the lee side of ridgelines or in confined gullies. You can use small test slopes or quick hand pits as you travel to see how the storm snow has bonded to underlying surfaces or if there are interstorm layers of concern. You may see it failing easily in blocks or notice cracking of the surface indicating a potential problem. If you notice these signs or get concerning results with your quick tests, avoid all slopes over 35 degrees.

    (3/24/2023)

    A shallow human-triggered slab in a confined chute on Mount Snoqualmie. 

    Photo: Jourdan Harvey

Avalanche Discussion

Even though the calendar has switched to spring, we’re in the midst of a more winter-like storm at Snoqualmie Pass. As of Friday evening, we have received around 5 inches of snow at lower elevations which increases to over a foot up higher. If the convergence zone alluded to above hits the forecasted water numbers, we could squeeze out another 5 to 10 inches by daybreak on Saturday.

You’ll likely encounter the most dangerous avalanche conditions first thing in the morning as this storm is wrapping up and the snowpack adjusts to the new load. As the day wears on, you may find that hazard transitions towards more specific terrain features or is more likely on wind-loaded slopes. On Friday, skiers on Mount Snoqualmie reported triggering a shallow slab in a confined chute. On open slopes at upper elevations, they also reported that the storm snow cracked and failed on the underlying sun crust. Alpental Pro Patrol observed both loose and slab avalanches running at the base of the storm snow and on an interstorm layer. 

Prior to the storm, mostly warm and sunny weather impacted the zone for the majority of the week. A surface crust formed on most aspects and elevations. The caveat is high-elevation northerly terrain where dry soft snow survived and possibly faceted (weakened) during this spell. Both of these surfaces could aid in avalanches failing on Saturday, so be sure to check the bond (3/22 interface) throughout your travels. All avalanche activity is expected to occur at or above this interface on Saturday.

As the storm winds down and becomes more showery, don’t be surprised to see a sun break or two. This could result in rollerballs or even a few Wet Loose avalanches. We have been concerned about larger Glide avalanches this past week due to the generally warm weather. It’s worth continuing to minimize your time spent under slopes that contain large Glide cracks on Saturday. It is spring, after all.

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