Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Tue
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

If you are planning on taking advantage of the nice weather on Monday to venture toward upper elevations, don’t be surprised to find a lingering Wind Slab. If you notice textured snow surfaces or firm, hollow-sounding snow, then head for lower angled slopes. 

Problemi valanghivi

  • Wind Slabs

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

    A strong wind event ripped through Snoqualmie Pass this past week and created some unusual loading patterns throughout the zone. We believe the most sensitive slabs to be on NE-N-NW aspects, but since we experienced a variety of wind directions, you should look for pockets of wind affected snow on all aspects. You are more likely to find these slabs as you ascend in elevation, with the possibility of them being large at higher elevations. You can look for smooth pillow-like piles of snow or textured surfaces to help you identify wind-loaded features. If you encounter firm, hollow-sounding snow, you could be dealing with more stubborn hard slabs. Use small test slopes to check the bonding and reactivity of these slabs. Look out for convex rollovers, the sides of gullies, or the base of cliffs where windblown snow often accumulates and you could trigger an avalanche more easily.

    (12/23/2020) Blowing snow from moderate southeasterly winds was forming thin new wind slabs. Chair Peak, 5200' N aspect.

Avalanche Discussion

The snowpack around Snoqualmie Pass contains an average of 20-35cm of snow over a prominent crust (12/21). Some areas have been stripped down to the crust by the wind, while other areas have wind drifted pockets as deep as 60-70cm. Below the 12/21 crust, the snowpack is generally strong and not of concern at this time. Any avalanche activity on Monday should occur above the crust, with avalanches possibly containing all of the recent snow. On Sunday, NWAC team members were able to confirm some weak snow grains above the 12/21 crust which could cause a point of failure. Alpental Pro Patrol recently had slabs release on these weak grains while large avalanches have been reported on this layer in the neighboring West South zone. These slides have been breaking in some surprising ways and are generally found on NE-N-NW aspects which have been wind-loaded.

If you climb out of the East flow clouds on Monday morning or find that the clouds dissipate and you are standing in the sunshine, there’s a chance you could encounter some Wet Loose avalanches. Keep your eyes open for new rollerballs or the snow surface becoming wet and sticky to help you identify that conditions are changing. If you see fan-shaped avalanche debris, head for shadier slopes. 

The 12/21 crust is very firm and travel conditions can be difficult because of it. Allow yourself extra time and look out for open creeks and other early season conditions at lower elevations.

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.

Regioni coperte