Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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In sintesi

Easterly winds may form shallow wind-drifted slabs, and you could trigger an avalanche. There is a chance that wind-loading might make larger avalanches on weak snow layers easier to initiate. Consider steering around steep slopes where you find deep drifts and cornice development, particularly on aspects and elevations that harbor a weaker snowpack. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Recently fallen low density snow is easily carried around by the wind, and wind coming from the east has a tendency to load surprising slopes and catch backcountry travelers off guard. Wednesday won't start out particularly windy but will pick up in the afternoon. Additionally, some slabs may have formed on Tuesday and will still have some heightened sensitivity. Although small, you could get knocked over and carried into hazards such as rocks and cliffs.

    Wind-loaded snow is often found just below ridgelines and in cross-loaded gullies. Red flags are cracks shooting out from your sled or skis and recent slab avalanches in similar terrain. Visual clues such as cornice development, rippled snow surfaces, and blowing snow will help direct you to the side of a ridgeline where wind-loaded snow may be lurking. If you find any of these clues in exposed terrain at middle elevations, there is a possibility of triggering an avalanche there as well.

    While less likely, a triggered wind slab could "step down" and become a more consequential persistent slab avalanche on slopes facing W-NE. Read below for more details.

    (2/9/2025)

    While most wind slabs appeared stubborn, there were a few sports that showed the ability to fail on uptrack tests 

    Photo: Joe Dellaporta

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1.5–2

    The likelihood of triggering a large and consequential avalanche is low but not impossible. We have not heard of any confirmed avalanches failing on buried weak layers in this zone, but we often have little data for this zone to support the forecast one way or another. What we do know is that poor snowpack structure still exists, and an uptick in easterly wind may have made lee terrain more problematic. 

    Persistent slab avalanche problems are tricky to manage. You may or may not see clear signs of instability - cracking, collapsing, or recent slab avalanches - before it's too late. Use the clues laid out in the wind slab problem to help you identify wind-loaded slopes and understand that a small wind slab avalanche can "step down" and trigger a more deadly persistent slab avalanche. You can reduce your risk by choosing slopes that are shorter, more planar, and free of hazardous cliffs or terrain traps. When in doubt, default to lower angle, sheltered terrain.

    (3/2/2024)

    An example of a persistent slab avalanche that occurred in the East South zone last season. The crown of the avalanche ranged from 2-4+ feet deep.

    Photo: Dallas Glass

Avalanche Discussion

Wednesday will be another cold day despite sunny skies. With this kind of weather, the ramifications of a backcountry emergency quickly increase, so be prepared with plenty of layers and hand warmers! Exposure to the sun may cause small loose snow avalanches to release, but the temperatures will moderate this problem throughout the day.

The likelihood of triggering a large persistent slab avalanche is decreasing, but the consequences have not changed. This problem has been especially unique due to the high variability of snowpack surfaces leading up to new snowfall at the end of January. Additionally, sustained cold weather has slowed down the healing process. This problem has many long time avalanche professionals still traveling conservatively despite the lack of recent signs of instability. Stack the odds by sticking to well-supported terrain and enjoying high-quality powder riding in more sheltered terrain.

Submit an observation to help NWAC Forecasters reduce uncertainty. It can be short, simple, and even anonymous. Any information you have will help us write more accurate forecasts.

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