Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You can trigger actively forming slab avalanches on steep, wind-loaded slopes near and above treeline.  Note and avoid wind-loaded areas where you find cracking of the snow surface, lense-shaped pillows, or beneath freshly forming cornices. A firm crust beneath the new snow will continue to create challenging travel conditions, make self-arrest more difficult and increase the consequences of any fall. 

Problemi valanghivi

  • Wind Slabs

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

    We're expecting 4-6 inches of low-density snow to fall at all elevations Thursday night and Friday which should be blown around by light to moderate winds. The storm snow will overlie 2" of snow above a stout crust.  Wind-affected snow will be the necessary ingredient to form a slab and thus wind slabs will be larger and easier to find as you head into more exposed areas at higher elevation. You are most likely to trigger a wind slab on a wind-loaded slope in the lee of ridgelines or where wind loads a steep, unsupported slope. Most of these avalanches will be small, but they may be large in the most wind-loaded locations. The new-old snow interface may be a subtle plane of failure or the slabs may fail directly on the crust. In either case, the crust provides an efficient bed surface, so avalanches may run farther than you expect.

    In less wind-affected areas lacking a slab, you can trigger a Dry Loose avalanche that runs faster than you expect slopes steeper than 35 degrees at any elevation. Consider the hazards below (trees, rocks, ice) in the event that a loose dry avalanche knocks you off your feet.

    (11/25/2020) Example: Small skier triggered wind slab (D1) on a wind-loaded slope.

Avalanche Discussion

Avalanche problems are limited to the new and recent cold snow.

Approximately 1.3" of rain soaked the upper snowpack at all elevations around Snoqualmie Pass Tuesday and Wednesday which has refrozen into a crust. You are likely to continue to find evidence of a loose wet and glide avalanche activity initiated by the rain event.  The loose wet avalnaches could create frozen chunks that could be dangerous, shallowly submerged within the recent snow. With several days of cold temperatures, the threat of glide avalanches should be very, very low. However, if you see crevasse-like glide cracks, give these slopes and areas below them a wide berth. Early Tuesday morning a smooth rock slab naturally avalanched at Alpental Ski Area and serves as a reminder that water can easily weaken the base of the snowpack. 

Recent weather wreaked havoc on the snow leaving us with variable and potentially difficult travel conditions. Firm surfaces abound under the recent fresh snow. Be confident in your ability to arrest in case of a fall. The snowpack at lower elevations eroded during the warm and wet weather amplifying early season conditions. You will likely encounter numerous open creeks, downed logs, and exposed obstacles. Give yourself extra time to deal with these demanding conditions.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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