Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Fri
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 avalanches in wind drifted snow on slopes 35 degrees and steeper. Be especially cautious around large convex slopes at upper elevations. Use visual clues to help identify and avoid unstable areas of wind loaded snow.

Problemi valanghivi

  • Wind Slabs

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

    Recent deposits of windblown snow still need time to settle and stabilize. With increasing southwesterly winds and plenty of snow available for transport, existing slabs could thicken and fresh slabs may even form. Wind slabs will grow in size and distribution as you climb up in elevation. Triggering an avalanche is most likely on north through east aspects above 4500ft near ridge crests, in gullies, and in unsupported terrain steeper than 35 degrees. 

    Pay attention as you transition into wind affected terrain. Watch for blowing snow, fresh cornices, and textured snow surfaces as good indicators wind slabs exist nearby. Assess new and wind drifted snow as you travel, and look for cracking, collapsing, and recent avalanches. Choose sheltered, lower-angle terrain to avoid the problem, and steer around convex rollovers and slopes below cornices.

    (11/23/20) Shallow wind slab (D1) failed naturally within recent wind drifted snow on a north aspect at 4500ft near Austin Pass

Avalanche Discussion

Over the past three days, the West North zone received almost 2in of water with fluctuating snow levels. This water translated into a few inches of cold snow Monday, rain up to 5000ft Tuesday, and 6-8in of new snow above 3500ft over the past 24 hours. Expect drier conditions on Thanksgiving Day with a slight chance for light precipitation and mostly cloudy skies.  

A handful of small, human-triggered avalanches (D1) were reported in the Mt. Baker area on Wednesday. The majority of avalanches failed within new snow 4-6in deep in northerly terrain above 4500ft. Avalanches did not entrain significant snow or run far downslope. Minor dry loose avalanche activity was reported as well. 

Generally, the new snow is right-side-up and well bonded to the old snow surface. Instabilities within new snow will be short-lived and confined to wind loaded areas at upper elevations. Snow depths range from 40-60in throughout the Hwy 542 and Hwy 20 corridors, and continuous snow begins near 2500ft. Snow coverage is well above average for this time of year, but early season conditions still exist. Stay alert for open creeks, tree wells, crevasses, or other exposed hazards. Consider the consequences when choosing terrain. Falling or getting caught in even a small avalanche could result in a rough ride.

Now is a great time to run through your safety equipment and make sure everything is in good working order. CLICK HERE for more information on early-season equipment checks. What did you see out in the field? SHARE YOUR OBSERVATIONS with NWAC and the backcountry community. Check out this BLOG POST and VIDEO TUTORIAL to find out more about why observations are so important and how you can view and share information on NWAC’s new public observations platform.

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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