Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
4 · Gross
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

7a Update- Less overnight snow than forecasted. Heavy snow and strong winds will create very dangerous avalanche conditions on Tuesday. Natural and human-triggered avalanches will be large enough to bury you. Avoid avalanche terrain at upper elevations, and stick to low-angle slopes in forested areas sheltered from the wind.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    1.5–2.5

    Many areas of East Central will get over a foot of new snow with ridgeline winds over 30mph. You should anticipate sensitive wind slabs developing in any terrain not sheltered by thick forest. These slabs will form over various slick or weak snow surfaces and may run farther than you anticipate. We expect large natural wind slab avalanches, particularly in alpine terrain. Avoid all avalanche terrain in areas where the wind has drifted snow. The most likely places for wind slabs to develop are near ridgelines, convex rolls, and the base of cliffs. Look for actively blowing snow and use visual clues, like textured surfaces and "fat" looking drifts, to identify stiff wind slab locations. Tuesday isn't a day to travel into wind-exposed terrain. Stick to forested areas, sheltered from these strong winds. 

    (1/29/2023)

    Like in this example, actively blowing snow is a sure sign of wind slabs on the slope below. 

    Photo: Dallas Glass

  • Storm Slabs

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

    Wind-loaded terrain won't be the only place to trigger an avalanche on Tuesday. We also expect gradually warming temperatures with high precipitation rates to form widespread sensitive storm slabs. While the snow totals aren't very impressive in the Wenatchee Mountains, a layer of buried surface hoar about 5 inches deep may make for sensitive storm slabs that propagate farther than you expect. Further west, these storm slabs may be up to 1-1.5ft deep. Look for clues to unstable snow, such as recent avalanches, shooting cracks, and collapsing. If you venture out into the storm on Tuesday, stick to simple terrain on low-angle slopes in forested areas.The bump in temperatures won't be the first warm-up that lower elevations have experienced. Still, new snow overnight with warming afternoon temperatures may make wet loose avalanches possible below 4000ft. So look for signs such as rollerballs and pinwheels to indicate these wet avalanches are possible. 

    (12/20/2022)

    Small test slopes that show mini avalanches are bullseye information that avalanches are likely. 

    Photo: Public Observation

Avalanche Discussion

A series of smaller storms brought refreshes of snow, but this storm will be the first major event since the MLK storm for the eastern slopes of the Cascades. The new snow will bury a complex array of surfaces, from stiff wind-board and slick crusts to weak faceted snow on high-elevation north aspects. This setup means snowpack conditions may become tricky even after this storm exits the area. While it will surely be a nice change back to deep powder riding and skiing, the snowpack will need time to adjust to this new load. We also need to observe how these deeper weak layers in the snowpack react and adapt to this additional snow.

Over the last few days, I have been to the westernmost and easternmost edges of the East Central zone. Not surprisingly, snowpack conditions in these locations are quite different. A deeper and stronger snowpack exists in the western portion of the zone, and further east, a shallower snowpack with more prominent and concerning buried weak layers. Common landmarks in these snowpacks are the MLK crust and the Christmas Crust, buried .5-1.5ft deep and 3-4ft, respectively. The recent cold weather weakened the snow above and below the MLK crust into weak, faceted grains, creating a weak structure that we'll watch closely after this storm.

In the lower Little Wenatchee River Drainage, I found 300cm of snow at 5600ft that increased in strength with depth. Just outside of the Mission Ridge Ski area on Sunday, I found 230cm of snow, and while much of the snowpack was strong 1F or P rounded grains, two prominent layers of buried surface hoar exist. The lower layer of surface hoar, buried on January 4th, is still producing propagating test results, despite being below the MLK crust. We are still tracking this layer but don't anticipate avalanche activity on this layer during this storm. However, a layer of surface hoar, buried on January 18th, may produce avalanches with this new snow load. So keep it in your mind, and choose conservative terrain, if traveling in the Wenatchee Mountains. 

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