Boletín de aludes

East Slopes North

Northwest Avalanche Center
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Peligro de aludes

Wed
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Expect dangerous conditions above about 5,000ft. Avoid steep slopes at upper elevations where westerly wind will drift stiff slabs of snow. You may find variable travel and avalanche conditions at low elevation. 

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2

    Very strong westerly ridgeline winds will continue to transport snow onto lee slopes. You'll find firmer wind-affected snow near and above treeline and even on open slopes well below treeline.  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.

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Above about 5,000ft, you could trigger avalanches in the storm snow.  Storm slabs will be possible where the recent snow is cohesive and you see cracks in the snow. As you work higher into the mountains, you'll find more light, dry snow. You could trigger loose avalanches in the most recent snow where it's uncohesive and slides easily. Avoid traveling over convex and unsupported terrain features.  If you see signs of instability like cracking or natural avalanches, stick to slopes under 35 degrees.

    1-2 feet of snow fell since the 21st with rain to about 4,500ft. Low elevation slopes may be rain-soaked. The snow that accumulates Monday night into Tuesday will be much drier and lighter than earlier in the storm. Use test slopes and quick snowpack tests to assess how this new snow is bonding. 

    (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

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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