Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Unstable slabs of wind drifted snow may be found near and above treeline. You will be entering areas of greater avalanche danger where you observe enough new snow to smooth over old, rain affected snow surfaces. Watch out for cornices or other unstable snow features in steep or rocky terrain above you.

Problemi valanghivi

  • Wind Slabs

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

    Continued precipitation associated with a Puget Sound Convergence Zone - plus lowering freezing levels - will allow 6" or more of new snow to fall this evening in some areas. Deeper new snow will be found in the southern portion of the zone along the Hwy 2 corridor and also as you travel to the northeastern fringes of West Central where temperatures are generally colder. Moderate to strong ridgetop winds can redistribute this snow to leeward aspects and build new wind slabs. Identify and avoid steep slopes with signs of recent wind loading if you make it to any of these areas on Friday.  Monitor new snow depth and the extent of wind transport as you ascend. Use visual cues like scoured snow surfaces and cornices to figure out where new unstable winds slabs may lurk. 

    (12/20/2021)

    Wind affected snow surfaces can help identify areas of wind slab. In this photo the wind was blowing from right to left. In the surrounding area terrain on the right was rocky and wind scoured and terrain on the left was smooth with no texture.

    Photo: Lee Lazzara

Avalanche Discussion

Rain will transition to snow on Thursday evening with freezing levels expected to drop to nearly 2000’ overnight. Over 3" of rain fell at lower elevations. No new avalanche activity was reported. 

Increasing sun in the afternoon will increase the possibility of loose wet avalanches on southerly slopes, especially above treeline where drier, newly fallen snow will be more susceptible to warming. Move to lower angle terrain if you witness signs of instability like rollerballs, a rapidly warming snow surface, or current avalanche activity. 

Another round of rain at lower elevations continues to weaken cornices and other overhead hazards clinging to very steep and/or rocky terrain. Be aware of and minimize time spent below unstable features you identify in the terrain above.

In addition to avalanche hazards, expect challenging travel conditions on frozen, uneven surfaces. Steep tree covered terrain has been noted as particularly difficult to navigate. If you haven’t made it to the mountains since the rain and warm temperature regime took over 10 days ago, be prepared to see a very different environment. Exposed rock, glide cracks, open creeks and a very rough snow surface all present new features to steer around.

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