Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sun
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

New snow and southwesterly winds may create fresh drifts in upper elevation terrain by Saturday morning. Large human-triggered avalanches are possible on leeward slopes 35 degrees and steeper. With clearing skies following the storm, keep wet loose avalanches in mind on sun-exposed slopes.

Problemi valanghivi

  • Wind Slabs

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

    Fresh deposits of windblown snow will be most reactive to human triggers below ridge crests, in gullies, and in unsupported terrain steeper than 35 degrees. Be especially cautious on north and east aspects above 5000ft. Monitor changing conditions as you climb up in elevation and transition into wind affected terrain. Use visual clues to help identify wind-drifted snow and look for sudden changes in snow surface texture and hardness. Carefully assess the upper snowpack as you travel, and look for cracking, collapsing, and recent avalanches. Blowing snow and fresh cornices are good indicators wind slabs likely exist nearby. To avoid the problem, choose sheltered, lower-angle terrain, and steer around convex rollovers and slopes below cornices. 

    (11/25/2020) Small skier-triggered wind slab avalanche (D1) on an east aspect near 5200ft on Tye Peak in the adjacent Stevens Pass zone.

  • Loose Wet

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

    Snow surfaces could heat up Saturday, but the sun will have to compete with clouds and some wind. It may not take much for the new storm snow to become wet and weak, and small wet loose avalanches are possible on steep sun-exposed slopes. Watch for dripping trees, pinwheels, and rollerballs as clues that wet loose avalanches may follow. Pay attention as conditions change throughout the day, and move to cooler, shaded slopes to avoid the problem. Be especially careful around large, rocky outcrops on SE-S-SW aspects that could shed snow onto slopes below.   

Avalanche Discussion

A frontal system looks to bring rain and snow to the Mountain Loop area with 2-4in of new snow accumulating by Saturday morning. Expect a cooling trend during the storm (5500ft snow levels dropping to 3000ft) and strong southwesterly winds overnight. Precipitation should taper off early morning Saturday with a chance for sunshine and 3000ft freezing levels during the day.

Observers on Green Mountain Friday reported wet snow surfaces and small loose wet avalanches on sun-exposed slopes. Cold dry snow could still be found on shaded aspects, with only minor wind effect observed near ridge crests. The recent snow from Wednesday's storm is right-side-up and generally well bonded to old snow surfaces. Snow depths range from 40-60in throughout the west slopes of the Cascades, and continuous snow begins near 2500-3000ft. 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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