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
2 · Moderato
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In sintesi

Deep and destructive avalanches remain a very real possibility, especially in the south and east portions of the zone. Approach terrain with a conservative mindset, and avoid traveling on or below large open slopes steeper than 35 degrees, even in runouts down on the valley bottoms.

Problemi valanghivi

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    3

    Neighboring zones to the south and east continue to report recent very large avalanches failing 10 or more feet deep on the mid-January persistent weak layer. Aerial photos of very large avalanches from last week's avalanche cycle show evidence that deep persistent slab avalanches failed in the West Central zone as well. The weight of just a person may not be enough to cause an avalanche on this layer, but cornice fall or smaller wind slab avalanches could add the needed weight to trigger an avalanche on this layer. Temperatures have slightly cooled since our prolonged warm stretch earlier this week, reducing the risk of cornices failing. However, continue to dial back your terrain selection and build in a wide margin for error. Even traveling along the valley floor well below treeline may seem safe but it is not. If there are sparsely treed or open slopes above you which eventually lead to large steep avalanche paths high on a mountainside, an avalanche failing up there could probably hit you. Take a look at the Highway 20 avalanche in the media gallery, and the Monte Cristo trail as examples, in the media gallery below. Seek out simple, lower angled slopes and avoid going into, or underneath open or sparsely treed terrain with those large start zones above you.

    (3/1/2021) This very large avalanche occurred on the east facing slopes near Peak 7185 south of Mt Misch (near Green Mtn). The crown line was estimated to be 10-15ft at its highest point, and 700-800ft wide. Photo: John Scurlock

  • Wind Slabs

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

    Wind slabs developed as we received the brunt of the snow and wind Thursday night and Friday. Avalanches in the surface snow layers up to around a foot deep could be large enough to bury or injure you. Strong winds redistributed snow onto leeward slopes and crossloaded features. Feel for stiffer snow and search for pillowlike or textured deposits of snow to determine where wind slabs are. Cornices have grown very large in recent days, and with more snow loading them they may fail, triggering very large avalanches on the slopes beneath.  Avoid wind loaded slopes steeper than 35 degrees. 

    You may find small-large wind slab avalanches on Saturday. Photo: Adam U

Avalanche Discussion

Several adjacent zones are in a prolonged period of unstable conditions with continued natural and human-triggered avalanches. We expect that conditions in the West Central zone are similar, 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. Above freezing temperatures in the last few days elevated concerns more, and temperatures are at least below freezing now, reducing chances of cornices failing. 

Reports of impressive deep slab avalanches continue to trickle in. Some of these include avalanches which closed Highway 20 near Newhalem for nearly a week, and very large natural avalanches from last week on Benchmark and Fortune Mountains just north of Stevens Pass in the West Central zone. The avalanche near Mt Misch north of Green Mountain (photo in Avalanche Problem 1) is alarmingly large.  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. On Sunday, a natural D3.5 occurred in upper elevation north-facing terrain in the Chiwaukum Range on the eastern edge of the Stevens Pass zone, as well as another D3.5 natural on Chair Peak (Source Lake) in the Snoqualmie Pass zone. See photos below for several of these large avalanches.

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