Lawinenlagebericht

West Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Strong solar radiation and warming temperatures will raise concern for wet avalanches and cornice fall. The potential for deep and destructive avalanches lingers, especially in areas east and south in the zone. Approach terrain with a conservative mindset, and avoid travel on or below large open alpine slopes steeper than 35 degrees.

Lawinenprobleme

  • Cornices

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Cornices will require extra caution on Wednesday. These unpredictable features loom in many upper elevation areas and will weaken in the strong March sun. If they fail, they could act as huge triggers on slopes below and result in very large and destructive avalanches. Give cornices a wide berth while traveling along ridgelines, and avoid exposure to all cornice features above. Recent deposits of wind-blown snow may still need additional time to settle and stabilize. Continue to steer around large wind-loaded slopes greater than 35 degrees, especially at upper elevations.

    (2/24/2021) Cornices have grown large over the past several weeks like this example near Del Campo Peak.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Expect warming temperatures and strong solar radiation Wednesday. Watch for snow surfaces to become wet and weak throughout the day as skies clear, with the best chance for wet avalanche activity in the afternoon. You are most likely to encounter loose wet avalanches on sun-exposed slopes, but all aspects are suspect with freezing levels rising to 5000ft. Rollerballs and pinwheels are a good indicator that loose wet avalanches could follow. Steer away from terrain traps like gullies or slopes above cliffs that magnify the consequences of even a small avalanche. Keep in mind that wet loose slides in motion could even trigger slab avalanches. Move to shaded or lower angled terrain to reduce your risk. 

    (3/2/2021) Large rollerballs on a NE aspect at 4800ft in Henry Creek in the Stevens Pass Zone. Photo: Adam Butterfield

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    3

    Neighboring zones to the south and east continue to report recent very large avalanches failing up to 10ft+ deep on the mid-January persistent weak layer. These avalanches are continuing to catch everyone off guard. Additional evidence of deep slab avalanches in the West Central was confirmed Tuesday with aerial photos of very large avalanches from last week's cycle. The weight of just a person may not be enough to cause an avalanche on this layer, but big triggers like cornice fall or surfaces avalanches in motion have us concerned. Warming temperatures and strong solar radiation are raising uncertainty and adding complexity. Wednesday will be a day to dial back your terrain selection. Seek out simple, lower angled slopes and avoid going into, or underneath open or sparsely treed terrain with large start zones above you.

    (3/2/2021) Aerial photo of a very large natural avalanche in the Benchmark/Fortune Mountain area in the southern portion of the West Central Zone. Photo: George Coiner

Avalanche Discussion

Several adjacent zones are in a prolonged period of unstable conditions with continued natural and human-triggered avalanches. Observations are limited, but similar conditions are suspected in the West Central, especially in the southern and eastern portions of the zone. The deep slab problem continues to pose high consequences and demands a conservative approach to terrain and travel choices. Another significant warm-up on Wednesday will only make matters worse. Stay observant, and keep your eyes peeled for signs of instability.  

Reports of impressive deep slab avalanches continue to trickle in, including very large naturals from last week on Benchmark and Fortune Mountains just north of Stevens Pass in the West Central Zone.  On Monday, WSDOT avalanche teams triggered an 8ft deep D3 avalanche on the southeast face of Rock Mountain east of Stevens Pass, along with several D2 soft slab and wet loose avalanches. In the Chiwaukums, a natural D3.5 avalanche occurred in upper-elevation north-facing terrain and is suspected to have run on Sunday. At Snoqualmie Pass, very large natural avalanches ran each of the past several days including an impressive D3.5 avalanche on Chair Peak. 

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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