Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

You can trigger an avalanche in recent, wind-drifted snow. Steer around steep slopes below ridges where the wind has formed drifts. There is still potential to trigger large and surprising avalanches on an old weak layer of snow, which should keep you off of steep northerly aspects. 

Problemi valanghivi

  • Wind Slabs

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

    Steer around slopes steeper than 35 degrees where the wind has drifted deeper pillows of snow. If you see recent avalanches or cracks shooting out from your equipment, stick to lower-angle slopes. Textured snow surfaces and fresh cornices can help identify wind-loaded areas. You can also use small wind-affected test slopes to see how the snow reacts. Snow that cracks and slides easily means you can trigger an avalanche on a larger slope. There is a chance that a smaller wind slab could step down to more deeply buried weak layers, becoming a very large and dangerous avalanche. 

    On the night of March 9th, 6-8" of new snow accumulated. Strong westerly winds formed slabs, and then eased by the morning of the 10th. On Tuesday, you can still trigger avalanches in these wind-drifted slabs. 

    (11/26/2024)

    Shooting cracks in wind-drifted snow. 7,200ft, W. West fork of Cedar ck

    Photo: Will Govus

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    The only way to manage this problem is to avoid steep slopes on northerly aspects at mid and upper elevations. Avalanches may be easier to trigger near exposed rocks or wind-loaded slopes. Persistent weak layers take significant time to gain strength. This problem requires careful decision-making and patience. While the likelihood of triggering one of these avalanches slowly wanes with time, the serious consequences remain. These avalanches could break across entire slopes and run long distances.  In two separate involvements near Harts Pass, snowmobilers were buried and one person was killed. This illustrates how the snowpack is shallower and weaker east of Washington Pass.  Near and west of Rainy Pass, avalanches may be less likely. 

    (2/28/2025)

    A large avalanche near Hart's Pass that caught 2 snowmobilers and resulted in one fatality on February 28th. 

    HS-AM-D2.5-R4-O. Cone Mtn, NE, 6,800ft

    Photo: NCH

Avalanche Discussion

On Monday, observers found 6-8" of new snow west of Washington Pass with less further east. They reported triggering wind slab avalanche (size D1.5) on an east aspect at upper elevations near Easy Pass.

A late February storm brought 18" of snow to the area and was followed by a prolonged warm weather into early March. This resulted in a widespread natural avalanche cycle, first persistent slabs, and then wet loose and wet slab avalanches. Observers reported many large to very large avalanches with widely propagating crowns. The weak layer (January Drought Layer) is buried 2–3 ft (70-100cm) below the surface in the Washington Pass and Harts Pass areas, and ~4' deep for areas further west. Snow profiles between 6000-7000ft show some rounding and strengthening of the JDL, but overall the snowpack has not changed significantly. The snowpack is shallower and weaker east of Washington Pass. Near and west of Rainy Pass, the weak layer is buried deeper and capped with a thick melt-freeze crust.

NWAC Forecasters visited the site of the avalanche fatality near Harts Pass that occurred on 2/28. You can read the initial observation here. 

 

You can help us gather more data by submitting an observation HERE or via the Avy App. 

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