Avalanche forecast

East Slopes North

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Expect dangerous conditions near and above treeline. Avoid steep slopes at upper elevations where over 2 feet of recent snow and westerly wind drifted stiff slabs. On Wednesday, it may become easier to trigger avalanches in the recent snow on steep sunny slopes.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Strong west and southwest winds transported snow onto lee slopes into Monday. 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.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    You could still 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 on steep, sunny slopes as it warms thru the day. 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. Over 2 feet of snow fell since the 21st with rain to about 4,500ft. 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

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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