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 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Easterly winds will be on a steady ramp up into the strong range with extreme gusts overnight. You will find stiff slabs of wind-drifted snow where you can trigger avalanches in atypical locations, such as further down the slope and on unusual aspects. Actively blowing snow, textured drifts, shooting cracks, and stiff hollow sounding snow are all signs of wind-loaded terrain where you should avoid steep slopes.

Problemi valanghivi

  • Wind Slabs

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

    On Monday, the east winds ramped up, drifting the recent snow over ridges and across slopes into wind slabs. You could trigger these wind slabs on convex rolls, below ridges, the base of cliffs, and cross-loaded gullies. Expect that with the easterly wind direction and speeds up to 40mph, you are likely to find wind slabs in unusual locations. They may form below typical starting zones and on aspects generally scoured from the dominant westerly winds. Also, look for wind slabs developing in sheltered terrain at lower elevations, like open glades in the forest. With northern aspects holding plenty of dry snow available for transport, these new slabs could be quite large. These fresh wind slabs will form over various surfaces, including slick crusts and weaker snow, so they could be quite sensitive to triggering. Look for actively drifting snow, textured surfaces, and "fat" looking drifts to identify steep slopes to avoid. Warning signs such as shooting cracks are bullseye evidence that the snow is unstable. 

    (3/27/2023)

    The east winds began drifting snow early in the day on Monday, expect this to continue through Tuesday.

    Photo: Trevor Kostanich

Avalanche Discussion

Even though it's the end of March, it's still looking pretty wintery out there. The end of last week brought 8-18 inches of new snow, and while a couple of sunny days had us thinking about wet avalanches and formed crusts on southern aspects, northern slopes still hold cold, dry snow. This easterly wind event and the cloudy forecast will bring another round of winter, so you should put wet avalanche problems and spring diurnal mindsets away for the next couple of days and refocus on cold, dry snow problems. Last week's snowfall overlays a melt-freeze crust on most aspects except high-elevation northerly slopes (3/22 interface). Multiple shallow (3-10") soft slab avalanches were human-triggered over the weekend, failing within or at the base of the recent storm snow. Most of these slides appeared to be on steep convex slopes or near rocky terrain, such as rocky chutes or the base of cliffs. Avalanche professionals and NWAC forecasters identified pockets of weak snow, with a few whumpfing collapses experienced on west aspects at mid to upper elevations. We had some concerns about weak snow buried during this storm. If it survived, the distribution is spotty at best, but it could explain some of the collapses or a few of the triggered slabs. We are continuing to gather more information about this potential weak layer in the snowpack. So be sure to check the bond on the 3/22 interface and the snow above it as you travel on Monday. We expect any avalanche activity to occur at or above this interface.

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