Boletín de aludes

East Slopes South

Northwest Avalanche Center
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Peligro de aludes

Wed
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

NW winds continue to drift snow on the lee side of ridgelines where slabs generally small slabs remain reactive to human trigger. Steer around steep, start avalanche start zones below sharply corniced ridgelines. If you find evidence of wind transport lower on the slope, keep your slope angle under 35 degrees.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Slabs formed by strong W winds Saturday night have started to gain strength and will be stubborn to trigger. However, light to occasionally moderate NW winds continue to tranport modest amounts of snow into the immediate lee of ridges where slabs should be most reactive. You should steer around these slabs where they intersect slopes 35 degrees and steeper, paying particular attention under fresh, sharp cornices. Other potential trigger locations include the base of cliffs where snow has accumulated more deeply and on steep rollovers in exposed terrain. You can gauge slab reactivity on small, wind-loaded test slopes. In your evaluation, shooting cracks, denser over less dense snow structures, or easy hand shears should dissuade you from stepping onto larger or more consequential slopes in that vicinity. 

    (1/21/2023)

    These cornice formations and textured surfaces are a good indication that wind slabs are present on this slope. 

    Photo: Katie Warren

Avalanche Discussion

Full sunshine after 10 AM on Monday likely formed rollerballs and small wet avalanches on SW-S-SE aspects. The same may be possible on steep slopes receiving strong sunshine. If the temperature feels warm, steep slopes facing the sun will respond and you should adjust to cooler more shaded aspects.

Before this storm, clear and cold nights most likely created weak surfaces with facets and surface hoar. Although we lack direct recent observations from this zone, we know these weak snow layers were common throughout the rest of the east slopes of the Cascades. This may have created a poor bond between the old snow and the recent storm snow. The strong winds associated with this storm may have destroyed these layers in some more exposed locations and left them intact in others. So while wind slabs are the primary concern, you should also monitor this recent interface. Before stepping out into more committing or steep terrain on Tuesday, take a minute to check the bonding of the new snow to the old surface to see if it fails easily wherever you're recreating. Use quick hand pits and small test slopes to observe how the recent snow reacts. Slopes with a weak interface between the old and new snow layer could break wider than anticipated.

Chances are you will encounter challenging travel across the zone on a stout rain crust from mid-January, just below recent new snow. You may find shallow conditions at lower elevations with many hidden hazards, like exposed or barely covered rocks or stumps.  

If you get into the East-South, please let us know what you see by submitting a public observation! 

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