Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Use caution when approaching slopes where you expect to find firmer wind drifted snow.  In isolated areas, fresh and shallow wind slabs may surprise you by breaking widely over terrain features.  Warning signs include whumpfing collapses, drifts of freshly blown snow, and a layer of weak, sugar-like snow over a crust roughly 6-12" below the surface.  

Problemi valanghivi

  • Wind Slabs

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

    Following 4-6" of new snow and moderate SW ridgeline winds on Tuesday, we know that shallow fresh wind slabs formed on open slopes near and above treeline.  As you start to transition both in elevation and aspect, look for evidence of firmer wind transported snow.  Wind slab avalanches will be more easily triggered where they overlie weak sugary snow.  Dig down up to 12" and look for weak sugary snow grains over the crust.  Avalanches may also run further downslope than expected over the firm early December crust. Give yourself an extra buffer while traveling along ridgelines and in terrain connected to steep open slopes above.  

    Sticking to treed terrain, lower angle slopes without significant overhead exposure or windward aspects will help you travel safely on Wednesday. 

    (12/12/2020) Human triggered Wind Slab on the north side of Chair Peak that swept two travelers off their feet.

Avalanche Discussion

Wednesday will offer a brief reprieve from our active weather pattern.  The avalanche danger will quickly rise Wednesday night as a stronger storm impacts the area. 

A thick freezing rain crust from December 9th can be found below 5,000ft and east of Washington Pass.  6" or less of new snow has bonded poorly to the crust.  In these areas, the slick crust creates challenging traveling conditions.  On Tuesday observers noted near the Pass proper and above 5500' a rougher melt-freeze crust with up to 10" (25cm) of snow on top.  Small natural storm slabs released below cliffs and one small wind slab avalanche was triggered along a ridgeline. 

The snowpack remains shallow at lower elevations, and early season hazards such as downed trees, rocks and creeks are plentiful. At lower elevations and steep slopes, dust on crust conditions may make for icy and/or tricky travel.

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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