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

Dry and wet avalanche problems likely await you in the mountains on Saturday. Slabs will be larger as you ascend above Friday's rain/snow line or in wind-loaded terrain. Springtime weather can lead to unusual avalanches, so make travel plans with plenty of options to avoid overhead hazards.

Problemi valanghivi

  • Storm Slabs

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

    Slab avalanches may be easier to trigger in the morning as an overnight storm wraps up.  After a generally warm Friday, temperatures should start to drop, which could result in lower-density snow on the surface. While this snow could fail in slabs or loose, you'll also need to look for deeper layers from the past several days as potential weak points in the upper snowpack. The rising and falling temperatures mean a new crust could exist below Friday night's storm snow, creating an excellent bed surface for avalanches to run on. Springtime weather has delivered periods of graupel, which can act as a short-lived weak layer. Use uptrack tests, small test slopes, and quick hand pits to gauge the upper snowpack's slab potential. If blocks fail easily in your tests, you find a poor bond at the new/old interface, or discover an upside-down snowpack (heavy snow over weaker snow), then you should avoid slopes over 35 degrees where triggering a slab is more likely. Expect slabs to be larger and more reactive as you ascend above Friday's rain/snow line.

    (3/21/2025)

    A natural large (D2) slab avalanche that failed on a steep convex feature above a gully in the Alpental Valley. Although it failed in dry snow as a storm slab, the debris has a wet avalanche feel to it.

    Photo: Trevor Kostanich

  • Loose Wet

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

    We've got dualing wet loose problems to deal with on Saturday. To start off, it rained on Friday. So lower elevations are wet and soggy, meaning you may be able to push wet snow on steep slopes to create an avalanche. Of course, we're on a cooling trend, so that moist snow could start to firm up or even have new snow over it. 

    Which leads us to option two. There's a decent chance of extended periods of sunshine on Saturday. You'll need to find areas that have dry snow on the surface, followed by enough sunshine to destabilize it. If that's the case, you may see rollerballs, pinwheels, or snow shedding from rocky ledges, meaning wet avalanches could soon follow.

    Wet loose avalanches often start at a point but fan out and grow in size as they descend, possibly even triggering slabs along the way. If Friday's moist surface freezes into a crust, there will be an excellent sliding surface for avalanches in scenario number two to run on. In isolated locations, wet loose avalanches could gouge down into older snow layers and grow large regardless of their initial trigger.

    (3/21/2025)

    Rollerballs, pinwheels, and other wet avalanche activity on Mount Snoqualmie. This was above the rain/snow line but the surface was still moist.

    Photo: Alex Blanck

Avalanche Discussion

We have had measurable precipitation almost daily for roughly a week and a half, resulting in several feet of recent storm snow. The winds have also been significant, drifting snow onto multiple aspects and creating thicker slabs. Before Friday, the storm snow was generally right-side-up and setting. Storm interfaces were highlighted in snowpack tests but did not show much propagation. However, Friday's warm storm threw a heavier load on top, and wind gusts were recorded as high as 75 mph at the top of Alpental. Numerous reports from avalanche professionals and backcountry travelers indicate that the storm snow is now upside-down. This could lead to an uptick in slab activity on Saturday on steep slopes. Those winds likely created fresh cornices at upper elevations. Give these ticking time bombs a wide berth by not traveling on or beneath them.

Rain soaked our snowpack lower down, and wet avalanche activity was reported. The weather on Saturday is a bit complex, with competing factors vying to influence the snowpack. You should keep an eye on the sky and note how the snow surface changes throughout the day. An atmospheric river is on tap for Sunday, which should decimate our snowpack. Saturday night may not be the time to take that winter camping trip. Avalanche hazard will quickly rise and become very dangerous once the next storm arrives.

Apart from the constant parade of storms in March, we've also seen an uptick in avalanche involvements around the state and within our zone. Numerous backcountry travelers were caught and carried within the last week - some were partially buried. Parties often described conditions as "sneaky" or "surprising" when recalling their experiences. Since the upper snowpack and weather are so variable, you should constantly reassess conditions throughout the day. Even if slopes appear similar, they may act in very different ways.

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