Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto last year. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Don’t let the abundant sunshine cloud your judgment on Tuesday. Large, deadly, and unpredictable wet avalanches remain a possibility. There isn’t a way to confidently manage this problem, so avoid being on or under any steep open slopes.   

Problemi valanghivi

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Wet avalanches should be shaping your travel plans on Tuesday. While the sun won't help matters, the danger will exist all day on all slopes, regardless of whether the slope is sunlit. Avalanche frequency may be on the decline, but the size of a slide could hold steady, or even increase. 3+ inches of rainfall from the storm will continue to migrate through the snowpack, testing its strength and stability as it percolates and pools. The full menu of wet avalanche problems—wet slabs, wet loose, and glide—all remain on the table. It is nearly impossible to predict when a given slope will reach peak instability for a deeper wet slab or glide avalanche. Often, large and deadly slides can occur days after rainfall ends. No refreeze and soaring temperatures will only add more fuel to the fire. Cornices could also fail in the heat and trigger a dangerous slide below.

    Even if you don't observe signs of previous large avalanche activity, a destructive slide could release on its own and without warning. Large avalanches are mostly likely to originate in the upper and middle-elevations, though they could easily descend thousands of feet down into the lower elevations. Be aware of what is above you, even if you can't see clearly into higher terrain, and don't linger in runouts. Even wet loose avalanches that start out small could gouge deeply into the snowpack and grow plenty large enough to bury a human.

    Due to the combination of consequence and unpredictability, the avalanche conditions on Tuesday won't be "manageable". The safest bet is avoidance. 

    (3/2/2025)

    A wet slab avalanche from the late February Atmospheric River in the East North Zone. These slides can run incredible distances, well into valley bottoms. 

    Photo: Katie Warren

Avalanche Discussion

Since noon on 3/23, roughly 3" of rain has fallen at all elevations. The few observations we have are notable. Debris from a very large avalanche on Granite was observed at 2000ft in elevation. The slide likely originated thousands of feet above and had to travel over approximately 1000ft of bare ground before it came to a rest, serving as an excellent illustration of what we mean when we warn about avalanches descending into the lower-elevations. Meanwhile, Summit Pro Patrol observed two glide releases at Alpental. We suspect to see evidence of fairly widespread activity once we are able to get a view of things.

Water takes time to percolate through the snowpack and there are many interfaces above the late February AR Crust where it could pool, destabilize the snow, and trigger an avalanche. At the lower-elevations, the snowpack is thinner, has seen more rain, and, as lysimeter data at pass level suggests, is draining through the bottom, likely limiting wet slab possibilities while leaving the door open to glide and wet loose. However, observations from middle-elevations suggest that some interfaces above the old AR Crust are only just starting to see moisture while the wetting front remains relatively high in the snowpack. The take-home is that the cycle likely hasn't yet run its course on every slope.

What does this mean for mountain travel? Until we get either proper refreezing or see clear evidence that water has drained past any pre-existing interfaces, there simply isn't any reason to confidently travel in or below avalanche terrain. 

Fortunately, the decision for tomorrow should be pretty simple. Avalanche conditions notwithstanding, you will find arduous, mushy travel conditions in the mountains. It could be a gorgeous day to bike, hike, sunbathe, or do just about any other recreational activity off the snow on Tuesday. 

Regioni coperte