Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

You could still trigger avalanches where winds drifted recent snow into deep drifts. The most likely locations to find unstable wind drifted snow will be in alpine areas on steep slopes below ridges, confined terrain features, and at the base of cliffs. Steer around steep slopes with stiff, textured snow drifts or stick to wind-sheltered areas. In the western edge of the zone, near Salmon la Sac, recent snow totals are significantly higher, and avalanches could be larger. 

Lawinenprobleme

  • Wind Slabs

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

    Strong westerly ridgeline winds drifted recent snow into stiff wind slabs, particularly at upper elevations. Locally elevated danger could exist near Salmon la Sac, with significantly higher snow totals from Monday night. The most likely locations to trigger avalanches will be steep slopes below corniced ridges. Also, look for specific terrain features such as the base of cliffs or confined chutes and gullies as prime locations for triggering these lingering wind slabs. There is a possibility that wind slabs could step down into deeper buried weak layers. This scenario would produce a much larger, surprising avalanche that could be unsurvivable. This problem is particularly concerning in areas near and around Stevens Pass. Although uncertainty exists, similar conditions could also linger in areas further east. With this increased uncertainty, travel with a conservative mindset and consider wider safety margins.

    Use visual clues such as textured surfaces and drifts around rocks and trees to identify wind slabs. You can also use your probe or pole to feel for stiffer snow over softer snow layers and use quick hand pits to observe how easily the wind-stiffened snow slides off deeper soft layers. If the surface snow slides easily or you see other signs of instability, such as shooting cracks, steer around these wind-stiffened drifts in steep terrain. 

    (2/9/2023)

    An intentionally triggered wind slab on a leeward slope from Feburary 9th after a significant storm. 

    Photo: Matt Primomo

Avalanche Discussion

A strong convergence zone set up over Snoqualmie Pass on Monday night and pushed significant precipitation over the Crest in the Salmon la Sac area, which picked up 8-10 inches of snow. Places further east did not quite get as much snow. Blewett Pass only picked up 1-3 inches, but the winds were strong throughout the zone, so you can expect to find wind-affected surfaces and "wind board" in open terrain. 

The forecast is for sunny skies on Tuesday, with daytime temperatures just a notch warmer than Monday. So small wet loose avalanches may run on steep southern terrain. Look for rollerballs and pinwheels as initial signs that wet avalanches are possible. These slides typically initiate from snow shedding off steep rocks or tree bombs hitting steep slopes with wet surfaces, so keep an eye on the type of overhead terrain you're traveling beneath. 

On Sunday, observers reported moist snow surfaces up to 7000 ft. Warm temperatures dropped below freezing, and with the lack of new snow, these wet snow surfaces are refrozen and present challenging travel conditions. So anticipate slippery melt-freeze crusts and refrozen "chunder" under the forest canopy. 

In the nearby Stevens Pass zone, there have been large avalanches with wide propagation, potentially on buried weak layers resting over stout crusts. On Saturday, a report came in of a rider triggering a slab avalanche on an ENE aspect at 5400 ft (observation). Another observation came in on Sunday evening of a widely propagating avalanche on the south aspect of Jove Peak ( observation here). While we are uncertain of the failure layers of these avalanches, it doesn't change how we treat this difficult persistent slab problem. We have not yet confirmed any avalanches on these layers in East Central, but we have been tracking weak snow over the MLK crust for some time now. On Saturday, NWAC forecaster Joe Dellaporta observed a propagating snowpack test result on this layer buried around 17 inches deep on Dirtyface Mountain. The difference between Stevens and East Central may simply be that there is less slab over these layers in East Central, and it could become a problem with additional snow load. These avalanche occurrences are worth noting if you plan on traveling along the western edges of the East-Central. You should consider the high consequences of triggering a larger and more surprising avalanche.  

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