Bollettino valanghe

West Slopes North

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
Open full map
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 will 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, keep wet loose avalanches in mind as the new snow may become wet and weak 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 4500ft. 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. 

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

  • Loose Wet

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

    Skies should clear following the overnight storm, with more sunshine than clouds expected Saturday. The new snow may quickly heat up and become wet and weak on sun-exposed slopes. Watch for dripping trees, pinwheels, and rollerballs as clues that loose wet 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.  

    11/23/2020) Example of rollerballs and pinwheels on a south aspect at 5200ft in the West North zone.

Avalanche Discussion

A frontal system looks to deliver 4-7in of new snow by Saturday morning in the Mt. Baker area. Expect a slight cooling trend during the storm (3500ft snow levels dropping to 2500ft) and strong southwesterly winds overnight. Precipitation should taper off early morning Saturday with mostly sunnies skies and 3000ft freezing levels during the day.

Observers in the Mt. Baker area reported 4-8in of recent snow above 4500ft on Friday. The new snow was moist, heavy, and well bonded to old snow surfaces. No new avalanches were reported, but poor visibility limited observations above treeline. A handful of small avalanches were reported in the Hwy 542 corridor since Wednesday's storm. Human triggered slab avalanches were small and shallow, failing within recent snow in northerly terrain above 4500ft. Wet loose avalanches were reported as well. It did not take much sunshine for solar slopes to become wet and weak and steep rocky areas to shed snow (observation).

Snow depths range from 40-65in throughout the North 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.

Regioni coperte