Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

As the storm begins to wind down the avalanche danger will slowly decrease. Don’t let this lull you into a false sense of security. Avoid common trigger points such as steep slopes below fresh cornices, convex rollovers, and terrain around rocks and cliffs.

Problemi valanghivi

  • Wind Slabs

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

    Shifting winds throughout the storm likely created a patchwork of firmer slabs near ridgelines, on exposed features, under cliffs, and along mid-slope gullies. Unfortunately, a few inches of light fluffy powder will probably hide this problem from your view. You’ll need to use larger clues to help you figure out where these slabs might lurk underneath the inviting soft snow. Look for cornices and larger drifts to help you anticipate which aspects and features concern you. Since these slabs could easily produce an avalanche big enough to kill you, consider simply avoiding any steep open slope where you suspect wind loading occurred. Instead, look for more sheltered or lower-angled terrain to avoid these sneaky wind slabs.

    (11/28/2022) Snow (or lack there of) in the trees can serve as a great clue to help you locate potentially wind loaded slopes. Photo: Dallas Glass

  • Storm Slabs

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

    Observations from Wednesday indicate several storm layers exist in the new snow and they produced natural avalanches. While these weaknesses should continue to gain strength, you may still trigger them on very steep slopes or convex rollovers. Because the Pass received so much snow, normal observations such as uptrack tests and even small slopes may not give you the most accurate information. As you travel take a moment to dig with your hand or shovel. See if you find strong over weak snow that you can make fail. If so, give the snowpack more time to heal before venturing into steep consequential terrain.

    (11/30/2022)

    Natural slab avalanches like this were observed by Alpental Pro Patrol Wednesday. Crowns were typically 12 inches. 

    Photo: Andrew Pierce

Avalanche Discussion

A bit of uncertainty exists in how much new snow the Pass may receive Wednesday night and Thursday. With cold temperatures in place, even modest precipitation amounts could easily add 4-8 inches of new snow. While this shouldn’t be enough to increase the avalanche danger, it may serve to add a bit of complexity to layering in the upper snowpack and the ensuing avalanche problems. 

So far this storm has brought 26 inches of snow, and counting, to the Pass. This has nearly doubled the snow depth at lower elevations! Alpental Ski Patrol reported several natural slab avalanches around 12 inches deep. These likely occurred during the height of the storm very early Wednesday morning. They also noted several layers within the new snow. A nearby avalanche professional also noted these weaknesses and they produced localized cracking.

Even though this has been a significant storm for mountains, early-season obstacles still exist. Open creeks, holes around rocks, and thinly covered bushes continue to make travel more difficult and hazardous.

Regioni coperte