Boletín de aludes

East Slopes Central

Northwest Avalanche Center
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Peligro de aludes

Fri
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The recent new snow and strong winds will maintain dangerous avalanche conditions at upper elevations on Thursday. You can trigger avalanches in fresh wind deposited snow or on steep, open slopes that harbor weak layers 1-3 feet below the surface. Simplify your terrain selection as you gain elevation and be on the lookout for small wet avalanches on sunny slopes. 

Problemas de aludes

  • Wind Slabs

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

    New snow accompanied by moderate to strong WSW winds have built wind slabs in exposed terrain across the zone. Expect these slabs to become larger and more widespread as you gain elevation into the wind zone. Some of these wind slabs could fail easily if they break on a crust or on deeper weak layers if you get unlucky. 

    You’ll typically find these unstable slabs beneath exposed ridgelines, below cornices, and on mid-slope convexities in exposed terrain. Use visual clues like blowing snow or textured surfaces to help you identify where the wind has been at work. Ripples, dunes, and sharp drifts are all clues of nearby wind slabs. Shooting cracks, whumphing collapses, and fresh avalanche activity are good reasons to default to less steep terrain. 

    (2/19/2025)

    It was easy to trigger cracks in wind loaded, unsupported terrain features on Wednesday.

     

    Photo: Payton Schiff

  • Persistent Slabs

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

    Recent new snow is adding weight to weak layers 1-3 feet below the surface. You can trigger avalanches that break roughly 1ft on more recent weak layers or more concerning, on weak snow from our January drought that sits 2-3 ft below the surface. The most likely place to get unlucky will be in wind loaded terrain, but don’t write off more wind sheltered, open slopes either.  

    You may or not receive any warning signs like cracking or collapsing before triggering a large persistent slab. Persistent Slabs can release in surprising ways, propagate widely, and release from a distance away. You can't assume that tracks on a slope means it is stable.  These persistent slabs surprise people every year. You can reduce your exposure by avoiding steep, open slopes that face NW-N-NE-E, especially if they appear wind stiffened.

    (2/19/2025) Photo: Payton Schiff

    Propagating test results on weak layers that were buried around February 13th. 

    E aspect, 5700 ft in the Salmon La Sac

  • Loose Wet

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

    The new snow will start peeling off solar slopes as skies clear. It may not take much time for the surface snow to react to clearing on south and west aspects. Rollerballs, pinwheels, and sticky-wet surfaces are precursors of wet loose avalanches. These likely won’t be big, but its best to not underestimate wet snow, especially in more radical terrain. Shift your aspect once you notice obvious signs of warming.

    (2/17/2025)

    An example of rollerballs shedding on sunny slopes after fresh accumulations. You may see this on Thursday. 

    Photo: Joe Dellaporta

Avalanche Discussion

While this wasn’t a big storm for the eastern mountains, it did provide a nice refresh of 6-9 inches depending on your location in the zone. On Wednesday, avalanche professionals from Mission Ridge to the Salmon La Sac reported reactive conditions in both the new and wind drifted snow. Notably, a NWAC forecaster traveling in the Salmon La Sac area also reported unstable, propagating test results on the 2/13 layer, which sits roughly 1 ft below the surface in this part of the zone. 

The big question moving forward will be if this new load will be enough to activate weak layers from our cold, dry stretch earlier last week or in deeper layers from our dry January.  It's hard to say, but any new load on a weak snowpack is a good enough reason to dial it back for a little while. 

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