Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

A natural avalanche cycle is expected at upper elevations Sunday due to additional heavy loading from new snow and wind. Avalanches could break several feet thick and run far distances. Travel in or below avalanche terrain is not recommended. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2–3

    Another 1-2ft of new snow over the next 24 hours will bring storm totals this past week to 3-4ft. Strong and variable winds will continue to blow snow and overload leeward slopes. At upper elevations, avalanches large enough to bury cars or break mature trees could run naturally. Previously formed wind slabs still need time to stabilize, and fresh slabs will continue to grow in size and distribution with additional new snow and wind. Underneath all the recent snow is a firm and icy crust buried on January 24th. Weak snow may be associated with this crust in isolated areas, and it is a good bed surface for avalanches. If avalanches step down to this layer, the results would be very large and destructive. Avalanches could break widely across terrain features and run full track to valley bottom. Avoid avalanche terrain during periods of heavy loading Sunday, and steer clear of wind-loaded alpine slopes.  

    (1/29/2021) A human triggered avalanche (D2) in Mazama Bowl on a north aspect at 5600ft. The avalanche failed on the 1/24 crust breaking up to 2ft deep, 40ft wide, and running 600 vertical feet.

  • Storm Slabs

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

    Soft slabs will thicken throughout the day and become increasingly reactive to human traffic. Natural avalanches will likely occur on slopes 35 degrees and steeper near and even below treeline. Peak instability will coincide with the heaviest precipitation rates, which look to occur Sunday afternoon. Slabs could fail on a variety of mid-storm interfaces, and a warming trend will create up-side-down layering with heavier snow Sunday atop lighter snow from Saturday. Loose snow avalanches may also continue to run far and fast. Keep these sluffs in mind as they could trigger slab avalanches as they run downslope or carry you into obstacles, and bury you in confined terrain. Seek out low-angle, supported slopes away from overhead hazard. 

    (1/30/2021) A skier remotely triggered this avalanche (D1) Saturday below Herman Saddle on a SW aspect near 5100ft. The avalanche broke 40ft wide and 8in deep within new snow, and ran 60ft downslope. Photo: Matt Lubar

Avalanche Discussion

Expect very dangerous avalanche conditions Sunday. The heavy snow and wind in the forecast should be reason enough to avoid avalanche terrain. Adding even more concern is lingering uncertainty about weak snow associated with the crust buried on January 24. Give the snowpack time to adjust. Only venture out during the storm if you are confident in your ability to avoid avalanche terrain. 

The Mt. Baker area received 14in of new snow Saturday bringing snow totals over the past week up to 2ft+. Observers reported touchy conditions throughout the West North Zone with natural and triggered avalanches in many areas up to destructive size 2. A handful of remotely triggered avalanches were reported as well. Avalanches primarily failed within new and wind drifted snow and deeper breaking on the underlying crust (observation). Loose snow avalanches were small, but ran fast and were easy to trigger in wind-sheltered terrain. Winds were strong and variable with plenty of wind loading and poor visibility. 

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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