Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Tue
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In sintesi

Fresh wind slabs will form on lee slopes near and above treeline Sunday night.  Steer around steep open slopes where you find firmer wind-stiffened snow.  Slabs may be larger and more consequential near the Cascade crest where more snowfall is expected overnight. 

Problemi valanghivi

  • Wind Slabs

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    • Limite del bosco
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    1

    Strong westerly winds will transport new snow onto lee slopes Sunday night and Monday.   While most wind slabs will likely be shallow,  slightly deeper slabs are likely to build closer to the Cascade crest.  As you travel, look for blowing snow along ridgelines, spindrifts loading slopes below cliff bands, and feel for textured wind-affected snow as you change aspect and elevation.  All of these signs will help you identify which slopes to steer clear of on Monday.  Wind slabs may be easier to trigger on northerly aspects where they build over weaker, older snow. 

    If traveling along ridgelines with large cornices make sure to stay well back from the edge.  Travelers are surprised every season when cornices break further back than they expect.  Cornice fall could trigger an avalanche on the slope below.

    (3/8/2021) An example of blowing snow forming wind slabs in the Hairpin Valley near Washington Pass.

Avalanche Discussion

4-6" inches of new snow may accumulate near the Cascade crest including the Washington Pass area through Monday morning.  New snowfall amounts should taper off for areas further east.  Moderate to strong westerly ridgeline winds are expected to be widespread and last into Monday morning across the zone.  While wind slabs are the main avalanche problem to keep on your radar,  there will may be sun breaks further east of the Cascade crest.  It's spring-time, so if the sun pops out for an extended time following new snowfall, expect wet loose avalanches to follow suit on steep sunny slopes.  If you are sinking into wet surface snow deeper than your ankle or you see rollerballs or pinwheels release naturally on sunny slopes, it's time to change aspect or move to lower angle terrain.  

Earlier this week, warm temperatures and sunshine formed surface crusts on most slopes up to about 6,500ft.  On Thursday, observers reported a large wet loose avalanche in the Cutthroat avalanche paths above Highway 20. Steeper northerly aspects and those at upper elevations may have held weak, dry snow that now makes up the 3/18 interface.  Since the beginning of March, the region has undergone a slow warming trend. Observers have reported loose avalanches (both wet and dry) and falling cornices. Cornices are very large and still loom on many ridges.  Most of the observations of cornice fall came early in the month, but we continue to receive occasional reports. The mid-January weak layer that plagued most of the Cascades for the month of February was much less of a factor near Washington Pass.

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