Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
Open full map
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Kernpunkte

The storm continues to overload a weak and complex snowpack. You're likely to trigger avalanches in the new snow, especially where the wind drifts snow into stiff slabs. It may now also be easier to trigger large, unsurvivable avalanches on deeper weak layers. Minimize your exposure to big avalanche paths and stick to lower angle, supported slopes.

Lawinenprobleme

  • Storm Slabs

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

    Sensitive storm slabs were widespread on Thursday, failing on the recent 1/16 interface of weak faceted snow. These instabilities can take more time than usual to heal, especially with a few inches of additional snow and warming temperatures. While these storm slabs are very soft, some still had surprisingly wide propagation. In areas where the wind drifts snow, stiff wind slabs could be very sensitive and much larger. Stay off of and well out from under start zones and large leeward avalanche paths. This is not a time to trigger an avalanche in wind-loaded terrain. See more below.

    With up to 10" of recent snow and more expected overnight, there is enough snow for avalanches in sheltered terrain, and winds will have plenty of snow to drift into slabs. While the immediate concern will be for triggering avalanches in these fresh slabs, don't rule out much larger avalanches. Any avalanche triggered in recent snow could step down to more deeply buried weak layers, become very large, and propagate across terrain features. 

    (1/18/2024)

    Although the recent storm snow is very low density with little slab structure, the very weak 1/16 interface produced surprisingly wide propagation on Wednesday. 

    Photo: Katie Warren

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Put a large buffer of terrain between where you travel and large avalanche paths, especially with leeward start zones and steep wind-loaded features. Only expose one person at a time to avalanche terrain. Stay well out from under steep overhead slopes.

    A complicated and problematic snowpack structure exists and has been speaking to us with signs of instability, like whumphing collapses, as recently as Sunday. We anticipate these avalanches are becoming easier to trigger, where you find significant new snow and wind drifted slabs. Slab avalanches could be anywhere from 2-4 ft thick and potentially propagate widely across terrain features. Unfortunately, this structure is widespread throughout the zone and in many parts of the region. Additionally, a layer of buried surface hoar from January 2nd sits an inch or two above a crust from December 30th and has been the culprit of several avalanches in the southern part of the zone. Persistent slabs take continued patience. So, your best mitigation tool is to stay off large, steep, and or unsupported slopes.

    (1/10/2024)

    Backcountry travelers near Lake Wenatchee remotely triggered this avalanche from a low angle adjacent slope. This avalanche ran on weak, facted snow over the Solstice Crust.

Avalanche Discussion

Wednesday's natural avalanche cycle was impressive. We were out in the Salmon La Sac area on Thursday, and while the avalanches we observed were small, they were everywhere! Finding any steep convexity that had not already naturally avalanched was difficult. So, I used the small amount of snow left to test the reactivity of this new snow a day after the storm. These makeshift test slopes easily failed above the old crowns on near-surface facets. Another NWAC forecaster in the Icicle Creek area reported a long shooting crack in wind-drifted snow. Observers in the Wenatchee Mtns reported sudden, easy failures in snowpack tests on old December facets. Near Hex Mtn, an observer reported numerous small wind slab avalanches. Backcountry travelers have continued to report notable signs of instability, such as collapses and propagating test results. 

Last week's storm dropped about 3ft of snow in much of the East Central, with about 1.5ft in the eastern Wenatchees. NWAC forecasters went to the lower slopes of Cashmere on Saturday and found small faceted grains over a crust above 3,000ft. Weak snow above and below the Solstice Crust is still producing propagating test results, and now we have another weak interface below this week's storm snow. All these layers have the potential to result in very large, widely propagating avalanches. The bottom line is that it's complicated out there and about to get even more tricky with warming temperatures setting us up for a significant change. So, it'll be best to step back in your terrain selection and stick to lower angle and well-supported slopes as we ride out this shift to more moderate, seasonally average temperatures. 

If you get out, let us know what you see by submitting a public observation!

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