Lawinenlagebericht

East Slopes North

Northwest Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Strong westerly winds Thursday night along with new snow will increase the avalanche danger on Friday.  Avoid steep open slopes below ridgelines where you find firmer wind-affected snow.  Travel cautiously in the far eastern part of the zone where persistent weak layers can be found  2-3 ft down.   

Lawinenprobleme

  • Wind Slabs

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

    Strong to even extreme westerly ridgeline winds will move new snow onto lee slopes Thursday night and for part of Friday.  You'll find firmer wind-affected snow near and above treeline and even on open slopes below treeline.  Shooting cracks or hollow-sounding snow are signs you could trigger an avalanche on similar nearby slopes.  Avoid open slopes steeper than 35 degrees where you find freshly drifted snow, sticking to lower angle or wind-sheltered terrain.  

    In wind-sheltered terrain and for areas near the Cascade crest, you may trigger a storm slab avalanche.  Steer around convex rollovers and very steep unsupported slopes in areas you find more than 6" of new snow.  Dry loose avalanches are possible on slopes steeper than 40 degrees with unconsolidated new snow.  Don't let a dry loose avalanche catch you off guard around terrain traps. 

    (1/31/2021) Cracks and a small chunk of a slab triggered in a drift on a leeward slope near treeline just east of Washington Pass. Photo: Josh Hirshberg

Avalanche Discussion

The recent 1-1.5' of storm snow in the Hwy 20 corridor is well settled as we begin a new storm cycle.  We have few observations from the above treeline elevation band regarding the extent or distribution of recent wind-loading.  This incoming storm appears to be a notch above the typical storm for the East North regarding post-frontal westerly winds. 

While persistent slab avalanches are unlikely, they're still on our minds in outlying parts of the zone west of Washington Pass and more recently in the eastern mountains. On Wednesday 2/17, an observation from the Twisp River drainage in the near treeline band found the mid-January facet/crust combo unreactive in snowpack tests and over 3 ft down.  Buried surface hoar slightly closer to the surface,  less than 3' or 80 cm down, showed sudden results in snowpack tests. No new or recent avalanches down to this layer or other signs of instability like whumpfing, or collapsing were noted.  Further west, the last persistent slab avalanche occurred near Rainy Pass on Feb 8th (see photo below). It is suspected to have run on the mid-January crust-facet layer about 2-3ft below the snow surface. 

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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