Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto last year. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You could still trigger avalanches in wind-drifted snow, particularly in terrain with confined alpine features or below sharp ridgelines. Consider choosing lower-angle routes through steep terrain with wind-textured surfaces. Very large avalanches on old snow layers are still a concern, so avoid steep northern aspects where these weak layers exist. 

Problemi valanghivi

  • Wind Slabs

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

    We expect most recently formed wind slabs are gaining strength, but you could still trigger a larger avalanche in specific terrain at mid and upper elevations. The most likely place for lingering wind slabs is steep, unsupported slopes at upper elevations, especially in confined gullies. Look for cornice formations and pillowlike drifts, or feel for stiffer snow layers to identify wind-affected terrain. Cracks shooting out from your equipment or recent avalanches are signs to avoid steep terrain. You can also use small wind-affected test slopes to see how the snow reacts, if the snow fractures and slides easily, avalanches are more likely. Smaller storm slabs or loose snow avalanches are possible in sheltered terrain.

    A smaller wind slab might step down to more deeply buried weak layers, becoming a very large and dangerous avalanche. 

    (11/26/2024)

    Example of shooting cracks in wind-textured snow. 

    Photo: Will Govus

  • Persistent Slabs

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

    With this low likelihood, high consequence situation, continue avoiding steep northerly slopes where you could trigger one of these massive avalanches. They may be easier to trigger near exposed rocks or on 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. 

    We expect this problem to become less likely as we transition out of this stormy weather. But with significant uncertainty, it's best to focus on the potential consequences and continue to travel conservatively. You may not receive any of the typical warning signs, like collapsing before triggering a slide, and 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

  • Loose Wet

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

    It won't take much time for the intense March sun to make wet avalanches possible on steep sunny slopes. Pay attention to overhead hazards from snow shedding off steep rocks and move to lower-angle terrain if you begin to see rollerballs or the snow feels wet and sticky. You might be more likely to trigger these avalanches where new snow rests over slick crusts. 

    More lengthy sun breaks are possible further east and south in the zone. 

    (2/10/2024)

    Small wet avalanches from warming temperatures. 

    Photo: Will Govus

Avalanche Discussion

Sunday should be a mostly dry day, but it won't be totally clear and short bursts of convective showers or periods of sun are possible. Ambient temperatures will be chilly, but the mid-March sun will feel warm if it makes a more prolonged appearance. 

Recent storm totals are between 1-2ft, but taper quickly to less than 1ft further east in the zone. Observers continue to report natural and triggered small wind slabs at upper elevations. Lower elevations have a thin melt-freeze crust that softened in the afternoon on Sunday. 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 near Washington Pass, but much 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. Aside from getting deeper, the weak layer hasn't changed significantly since the active avalanche cycle. 

As a reminder, on Monday, March 17th, WSDOT crews will begin clearing the road from Silverstar Snowpark and snowmobile access to Washington Pass will end for the season. For more information, check out https://wsdot.wa.gov/

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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