Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Fluffy snow is hiding buried weak layers capable of producing a dangerous avalanche. Avoid this hazard by keeping off steep open slopes facing west, north and east. Safer avalanche conditions and incredible snow quality can be found on lower angle slopes and in forested terrain.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2

    1 ½ to 3 ½ feet of snow sits atop the January Drought Layer (JDL) and the 1/10 complex, and both harbor weak faceted snow and crusts. It has been close to a week since the last reported avalanche occurred on one of these layers, however, poor test scores continue to point to an untrustworthy snowpack. The snowpack has clearly communicated that all is not well, though the distribution of the unwellness is hard to pin down. The likelihood of triggering the persistent slab may be low, but that’s of little comfort if you happen to be the one that goes for the ride.

    Because of the spatial variability with this problem, it’s not possible to determine with certainty which slope is okay and which may slide. The only surefire way to manage the hazard is through a disciplined tour plan that avoids steep and open shaded slopes.  

    If you decide to roll the dice, stack the odds in your favor. Choose planar and supported terrain with clean runouts, no terrain traps, only expose one person at a time, and minimize your exposure on the ascent. Areas where the slab is thinner, such as around rocks, trees, and locally wind-scoured spots may act as trigger points. Be especially wary of these specific features within wind-loaded start zones. Complex terrain often holds this dangerous combination of thicker and stiffer slabs with locally thin areas on the slope.

    (2/3/2025)

    A skier triggered persistent slab avalanche near White Pass. This slide released over a 100ft wide and 2-3ft deep. This is the type of slide we are concerned about at the Pass.

Avalanche Discussion

Other than excellent snow quality, we have little new information from the Pass. With quiet and cold weather, we don’t expect anything much to have changed. We still don’t fully trust this snowpack and probably won’t for a while yet.

On Tuesday, a few other things could impact your day. Expect very cold temperatures, especially when you factor in the wind chill. Plan accordingly and appreciate what that could mean in the event of an accident. Increasing overnight winds could form shallow wind slabs before daybreak. Identify and steer around freshly wind-loaded slopes by looking for textured snow surfaces and lens-like deposits. In addition, fresh snow will see sunshine for the first time and a loose avalanche or two could come down. They shouldn’t be particularly impactful unless they knock you off your feet in a critical location.

A final thought related to the persistent slab and snowpack tests. Where the ECT asks “Can I break it, and if I do, will it propagate”, the PST asks, “When I break it, will it propagate”? As the slab gets thicker and stiffer, the latter may be a more appropriate question, as one can always find the thin spot. Lastly, an unstable test result should be a red light, but a stable test should never be used as a green light. Test for structure and instability, not stability.

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