Boletín de aludes

Stevens Pass

Northwest Avalanche Center
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Peligro de aludes

Fri
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You can still trigger a deep persistent slab in steep, upper elevation terrain. Identify heavily wind loaded features to consider staying away from. Wet loose avalanches can occur on slopes in the sun with rising temperatures during the day. Pay attention to moistening snow surfaces, opting to navigate around slopes that show signs of warming. 

Problemas de aludes

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–2.5

    The heavy snow and wind loading from the last weak has continued to stress a deeper weak structure. These layers consist of facets and crusts buried in early February or mid February. Avalanches that run on these layers can grow to become very large, as they're 3-4ft deep and can propagate widely across the slope. You won't get signs of instability before triggering one, as the layer is just too deep. Snowpack tests can identify the layers, but have become inconsistent from one slope to the next. You're best bet is to remain aware of the terrain around you, staying out of complex alpine terrain and off steep unsupported, or heavily wind drifted slopes. 

    This problem is more pronounced at upper elevations, and further east in the zone. Tuesdays large avalanche shows that they can still be triggered. 

    (3/5/2024)

    A large rider triggered deep slab on a W aspect of Jim Hill at 6,500ft. 

    Photo: Nate Hough-Snee

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Direct sun and slightly warmer temperatures may create wet loose instability on steep slopes. You can anticipate this problem by considering your aspect vs. timing of when you might be on any given slope. Look for signs of instability, like small rollers falling out of trees or small fan shaped slides. Feel for moistening snow surfaces on slopes in the sun. You can use test slopes to check and see how any given area might react. These slides should remain small, but may be able to entrain more than you'd think, especially in larger terrain features. 

    Example wet loose avalanche from last season.

Avalanche Discussion

We're in for yet another beautiful winter day with great riding conditions on many slopes. A party of three skiers triggered a deep persistent slab on Tuesday on the summit pyramid of Jim Hill, a NW aspect at 6,500ft. The slab was approximately 100ft wide and 3ft deep, and carried one skier approximately 200ft down the slope. The skier was fully buried, but recovered within a couple minutes with a minor injury. The strengthening March sunshine is starting to have more of an affect on snow surfaces. Plan your day to move away from slopes in direct sun, and keep checking for moistening snow surfaces as the day progresses. Since the 24th, the Stevens Pass area has received about 5" of water equivalent, and the snowpack gained 3-4 feet. 

On Sunday I investigated a D2.5 (large) avalanche on Jim Hill at 6,200ft, NE. It failed on the weak, faceted snow above the Early February Crust. Another forecaster visited Big Chief on Sunday and dug several pits on different aspects around 5700ft. She found inconsistent results, yet both facets above the Early February Crust and the 2/24 layer were noted and produced test results (compression, deep tap moderate-hard) in some of the pits. At Skyline on Friday, forecasters found a crust/weak layer, just below the February 24th interface to show a high potential for propagation.  

Your avalanche, snowpack, or weather observations are extremely valuable to the avalanche community. Help create a more accurate avalanche forecast by submitting your observations here. 

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