Lawinenlagebericht

East Slopes North

Northwest Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Increasing wind and snow will make it easy to trigger avalanches in wind-drifted snow. Avoid steep slopes below ridgelines and exposed terrain with pillow-like drifts. Steer clear of steep north-facing slopes where very large avalanches on old snow layers are possible. Instead choose wind-sheltered and low angle slopes to enjoy the fresh snow. 

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–1.5

    With another round of snow and wind, you can expect fresh, sensitive wind slabs at all elevations. Avoid likely locations for wind slabs, such as steep lee slopes below ridgelines and cross-loaded gullies. Cracks shooting out from your equipment, actively blowing snow, or recent avalanches are all important signs of instability. You can also use small wind-affected test slopes to see how the snow reacts. Snow that fractures and slides easily means avalanches are more likely. Smaller storm slabs or loose snow avalanches are possible in sheltered terrain.

    Use visual clues such as textured surfaces, cornices, or drifts around rocks or trees to identify wind affected snow. Stick to wind-sheltered terrain or low angle slopes to avoid triggering avalanches while you enjoy the fresh snow.

    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. 

    (11/26/2024)

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

    Photo: Will Govus

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Terrain avoidance is the only way to manage this problem, so continue to steer clear of steep slopes on northerly aspects at mid and upper elevations. Avalanches may be easier to trigger near exposed rocks or wind-loaded slopes. Persistent slabs are a tricky problem that take a long time to gain strength and require patience along with careful decision-making. The recent snowfall and significant wind-loading could be making these avalanches more likely, and the consequences remain serious. These avalanches could be unsurvivable, breaking across entire slopes and running long distances.  In two separate involvements in late February near Harts Pass, snowmobilers were buried and one person was killed. More recently, observers in this area found test results showing that the weak layer hasn't gained strength.

    (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

Expect light snow with moderate to strong winds throughout the day on Saturday. Wind slabs will build quickly and we expect that there could be some natural wind slab activity at upper elevations during the day. Thursday's older wind slabs are likely gaining strength, but this next storm will form another round of sensitive wind slabs. 

In areas further east, there is a chance for some clearing in the afternoon. If you start to see rollerballs or wet loose avalanches on steep sunny slopes, move to shady or lower angle terrain.

On Thursday, observers triggered several small wind slab avalanches at upper elevations in the Highway 20 corridor. Observers at Harts Pass reported cracking in wind drifted snow. They also found large and small column tests indicating that propagation is likely on the January Drought Layer. That said, their tests also indicated that you may need to find a shallow area to trigger the weak layer. 

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 2–3.5 ft (70-120cm) below the surface in the Washington Pass and Harts Pass areas. Near Rainy and Easy Passes, the JDL is over 4 feet deep and capped with a thick melt-freeze crust. Aside from getting deeper, the weak layer hasn't changed significantly since the active avalanche cycle. 

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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