Lawinenlagebericht

East Slopes North

Northwest Avalanche Center
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Lawinengefahr

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

Expect dangerous conditions near and above treeline where west wind will build fresh slabs through the day. Avoid wind-loaded slopes steeper than 35 degrees at upper elevations. You may be able to trigger small loose avalanches on steep shaded slopes below treeline. 

Lawinenprobleme

  • Wind Slabs

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

    Strong west winds will transport snow onto lee slopes on Thursday. You'll find firmer wind-affected snow near and above treeline where you can trigger the biggest and most dangerous avalanches.  Shooting cracks or hollow-sounding snow are signs you could trigger an avalanche on similar nearby slopes.  Steer around obvious wind features,  thickly loaded leeward slopes, and unsupported features. When in doubt, defer to lower elevation, wind-sheltered terrain and slopes under 35 degrees.

    Example of active wind drifting snow. Notice the fracture near the edge of the wind lip, indicating touchy conditions.

  • Loose Dry

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

    You could trigger avalanches in the storm snow.  Use caution on convex and unsupported terrain features and around terrain traps like gulleys and cliffs. As you work higher into the mountains, you'll find more light, dry snow. Use test slopes and quick snowpack tests to assess how this new snow is bonding. Expect about 5" of accumulation throughout the day. This will add to over 2 feet of snow fell since the 21st with rain to about 4,500ft. 

    (1/31/2021) An example of storm snow that slides easily and could result in an avalanche on slopes steeper than 35 degrees. Photo: Josh Hirshberg

Avalanche Discussion

Observers reported a cycle of avalanches up to size D2.5 that ran during the day and into the night of the 22nd. Most were near and above treeline at the base of cliffs, though some may have been in wind-sheltered terrain. One notable slide was 1-2ft deep and propagated 300ft across. It appears that all avalanches ran within the recent snow or at the interface of new and old snow. 

Persistent slab avalanches are still on our minds in the eastern mountains. On Saturday, an observed noted snow fracturing easily on a sun crust, others found shooting cracks, and others large dry loose avalanches. 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. This layer may again be a problem in the outlying eastern parts of the zone. 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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