Boletín de aludes

East Slopes Central

Northwest Avalanche Center
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Peligro de aludes

Sat
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Another round of light precipitation and moderate winds shifting back southwesterly will maintain the possibility of triggering shallow slabs in wind drifted snow. Look for textured surfaces and deep, rounded drifts to identify where these slabs may exist. Steer around these stiff pillows of snow in steep terrain. 

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Light precipitation will continue overnight and into the morning hours of Friday, with moderate winds out of the southwest. Winds in the last 24 hrs have shifted from easterly back to westerly, and wind slabs are likely present on all aspects. Observations from Thursday showed wind affected surfaces even down into lower-elevation forested areas. Observations from northern aspects indicated these slabs were shallow and stubborn to trigger, while southern aspects showed signs of this shallow new snow being more reactive. The size of these avalanches is likely on the small side. However, be wary of gullies, cliffs, or extreme terrain where the consequences of even a small avalanche could be significant. Look for textured surfaces and active transport to identify potentially wind-loaded terrain. If you observe signs of instability, such as shooting cracks within wind stiffened snow, avoid steep slopes or move to more sheltered areas. Before this storm, various weak surfaces existed with faceted snow, surface hoar, and surface crusts at lower elevations and southern aspects. These weak interfaces could have survived in some locations, and wind slabs may rest over weak or slick surfaces. Adjacent slopes with slightly different aspects may have variable stability.

    (1/5/2023)

    Cracks that shoot out from your skis, snowshoes, or snowmobile in wind-stiffened snow are a common sign of reactive wind slabs. 

    Photo: Katie Warren

Avalanche Discussion

Observations from Blewett Pass and Mission Ridge on Thursday were of 3-5 inches of new snow that was largely unreactive. Observations from South facing aspects near Lake Wenatchee demonstrated new snow sliding easily on the underlying melt-freeze crust that formed during clear sunny weather over New Years' weekend. There currently is little danger with the limited amount of new snow. Still, this weak interface (1/4/23) from Wednesday night's storm will be one to watch as we incrementally increase the overlaying snow depths moving forward. 

This recent 3-5 inches of snow covered widely variable old snow surfaces. Including the following.

-Wind stiffened snow in exposed terrain.-Sun crusts on southern aspects.-Rain/Freezing fog melt freeze crusts at lower elevations.-Weak, faceted snow and surface hoar in sheltered northern locations.

These variable old snow surfaces create a variably bond with the new snow. Use quick hand pits and small test slopes to observe how well the new snow bonds to underlying surfaces. Take notes on aspects and elevations where these few inches of new snow slide easily. As storms bury these layers deeper, they could become more problematic.  

Warm temperatures could bring rain to lower elevations trailheads, and small wet loose avalanches may be possible in very steep terrain.

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