Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

On Saturday, you will be able to trigger avalanches in the recent snow on slopes steeper than 35 degrees. Avalanches will be bigger and easier to trigger at middle and upper elevations. Avoid steep north aspects, in locations north and east of Mazama, where there is still a chance of triggering a very large, consequential avalanche in old snow layers. 

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    You can trigger avalanches in the new and recent snow on a variety of steep slopes. Avalanches were very easy to trigger on Friday. You may still be able to trigger these slides on the same interface ~8-12" below the surface. The most dangerous areas will be on leeward, wind-loaded slopes, just below ridges, or at the base of cliffs. While snowfall is expected to taper off Friday night, the wind will continue to drift snow through Saturday at upper elevations. Use small test slopes to observe how the snow reacts, before traveling onto slopes that are big enough to bury you. Recent avalanches, snow that slides easily, and cracks shooting out from your equipment are signs to avoid slopes steeper than 35 degrees.

    Winds out of the southwest have transported snow in the past 24 hours and will shift to the west, continuing into Friday night and Saturday. In addition to nearly 1 foot of snow that accumulated on Washington Pass on Friday, expect another 2-4" by Saturday morning. Fresh slabs in wind-drifted snow may be the most reactive areas today. You  just below ridges 

    (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

The stormy trend of the past 12 days is expected to continue this weekend. Recent storms have totaled 2 feet near Washington Pass with less further east in the zone. On Friday, the 21st, observers near Silver Star Mtn reported 1 foot of new and widespread natural and triggered avalanches in the new snow. Many were small (D1), but a number of avalanches were big enough to bury or kill a person (D2).  These occurred in both leeward, wind-loaded slopes as well as sheltered terrain. On the 20th, observers on Silverstar Mtn reported natural wind slabs and loose dry avalanches at upper elevations. They triggered shooting cracks and observed southwest wind transporting snow at ridge tops. In the past week, observers have reported a number of small natural and triggered wind slab avalanches. 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.

An old weak layer (the January Drought Layer) is buried 2–3.5 ft (70-120cm) below the surface but shallower east of Mazama. 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, the weak layer has rounded and gained strength. In the past week, observers have continued to report snowpack tests that have produced sudden and propagating results on Silver Star Mountain and near Harts Pass. The signs of instability and much shallower snowpack (see profile below) near Tiffany Mtn indicate more dangerous conditions in the far eastern mountains.

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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