Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

You can trigger avalanches in wind-drifted snow at middle and upper elevations. Steer around steep terrain below ridgelines and on cross-loaded slopes. Avoid steep north aspects, especially north and east of Mazama, where there is still a chance of triggering a very large, consequential avalanche on old snow layers. 

Problemi valanghivi

  • Wind Slabs

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

    Ongoing wind and a few inches of new snow will be enough to form fresh slabs on leeward sides of ridges. Look for blowing snow and cornices that point to the wind-loaded slopes. Recent avalanches and cracks shooting out from your equipment are signs to avoid slopes steeper than 35 degrees. You can also use small wind-affected test slopes to observe how the snow reacts. If the snow fractures and slides easily, you could trigger an avalanche on a larger slope. 

    (3/18/2025) Recent natural wind avalanches in very steep terrain in the Eight Mile drainage.

    Photo: Will Govus

  • Persistent Slabs

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

    In the north and eastern portions of the zone, you may still be able to trigger large avalanches on an old, weak layer about 3 feet below the surface. The snowpack is shallower, and the layer is more well-developed near and east of Harts Pass and Mazama. Further west, near Washington Pass and Rainy Pass, these avalanches are unlikely.

    That said, the current gusty storms are adding enough stress to the snowpack that we can't write off persistent slabs altogether. You can deal with this low likelihood, high consequence situation by avoiding steep northerly slopes with shallow and variable snow cover in the eastern part of the zone. You can dig profiles and use snowpack tests (deep tap and propagation saw tests) to identify the weak layer. When in doubt, defer to lower-angle slopes and simpler terrain.

    (3/17/2025)

    A widely propagating avalanche near Tiffany Mtn.

    Photo: Willie Webster

Avalanche Discussion

Thursday will bring another gusty day of westerly winds and a couple inches of snow. Recent storm totals near Washington Pass range from 1.5 to 2 feet, but taper quickly further east in the zone. In the past week, observers have reported natural and triggered wind slabs at upper elevations. On March 17, an observer near Tiffany Mountain reported widely propagating recent natural avalanches and rolling collapses on a weak layer in the middle to lower half of the snowpack.

A late February storm brought 18" of snow to the area and was followed by prolonged warm weather into early March. From February 23rd to at least March 3rd, this resulted in multiple widespread natural avalanche cycles, starting with 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 2–3.5 ft (70-120cm) below the surface near Washington Pass, but shallower further east and north. Near Rainy and Easy Passes, the JDL is over 4 feet deep and capped with a thick melt-freeze crust. In many parts of the zone, it's become difficult to trigger this weak layer. On March 12th, observers near Harts Pass reported large and small column tests indicating that, if triggered, propagation is still likely. We believe persistent slab avalanches are still possible in areas with a shallow and weaker snowpack in the north and eastern parts of the zone.

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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