Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Warm temperatures may produce another round of wet loose avalanches. You may find these wet loose slides on shadier slopes since freezing levels will climb near ridgetop level. Look out for lingering pockets of wind-drifted snow that could break in surprising ways if they step down to weak snow sitting over a slick crust.

Lawinenprobleme

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    Climbing freezing levels along with some filtering sunshine may allow for another round of wet loose avalanches. The difference this time will be the freezing levels jumping up to 6500 ft, so you may see these wet loose slides initiating on shadier slopes.  Look for pinwheels or rollerballs initiating on steep slopes as the day progresses. These are often precursors of wet loose avalanches and should be clear signs for you to move to lower angled slopes. 

     

    (1/25/2023)

    You may be able to trigger small wet loose avalanches like this, but on more unusual aspects like East and North as well. 

    Photo: Katie Warren

  • Wind Slabs

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

    You can still trigger a slab avalanche in areas of wind-drifted snow- especially if these slabs sit over weak surfaces that are now buried under the recent new snow. In this case, these avalanches could act in surprising ways and propagate widely. Feedback may be minimal, so your best bet will be to stick to well-supported terrain and avoid steep wind-drifted slopes. 

    Look for these wind slabs at mid and upper elevations, but more specifically on the leeward side of ridges, the top of chutes/couloirs, under cornices, and convex rolls in the alpine. Avoid steeper lines if you see signs of unstable snow, such as shooting cracks or hear audible whumphs. 

    (2/9/2023) View to the north. E at 6,500ft. Photo: Matt Primomo

Avalanche Discussion

On Saturday, I traveled near Lake Wenatchee to investigate how the new snow is bonding with the old snow surface. Above 5000 ft, I found approximately 12 inches of new snow sitting on the new/old snow interface. Snowpack tests produced sudden planar results, but no propagation on this layer. However, I did get propagation on a layer of weak, sugary snow above the MLK crust about 17 inches below the snow surface. In the neighboring Stevens zone, a report came in of a rider triggering a slab avalanche likely failing on the MLK crust on a ENE aspect at 5400 ft. Information on this limited, but worth noting  especially if you find yourself traveling along the western edges of the East-Central. 

On Thursday the new snow was still quite reactive in the upper Icicle drainage, with multiple ski triggered slides reported. These were on north to southeast facing terrain at and above 6,000ft. Some were in open areas in the trees, not just heavily wind affected slopes. Observers also reported whumphing collapses on wind affected ridgelines in the Teanaway that day. The culprit for the recent activity has been the old/new snow interface, which often consists of small grained faceted snow and is about 1-1.5 feet deep. Strong westerly winds substantially built cornices in places they were otherwise not very impressive before this storm.

Common landmarks deeper in the snowpack are the MLK crust and the Christmas Crust, buried 1.5-2.5 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're still watching. On Stevens Pass, ski area control work and a few natural avalanches ran down to the MLK crust on the 8th.

In the eastern Wenatchee Mountains, 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. A layer of surface hoar, buried on January 18th may produce avalanches with the newer snow load on top. So keep it in your mind, and choose conservative terrain if traveling in the Wenatchee Mountains. 

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