Boletín de aludes

Stevens Pass

Northwest Avalanche Center
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Peligro de aludes

Wed
Alta montaña
2 · Moderado
Límite del bosque
1 · Débil
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Expect a mild, cloudy day with clearing east of the Cascade Crest. If you hit the wrong spot, you could trigger a large and surprising slab avalanche on shaded, northerly aspects. Continue to keep your distance from large, steep slopes at upper elevations.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1.5–2

    There's still a chance that you could trigger a surprising slab avalanche, especially on slopes where the wind recently loaded snow at upper elevations. Use caution on leeward sides of ridges that hold recent drifts from winds on Friday night and Monday. Watch for "red flag" signs like whumphing collapses, cracks shooting through the snow, and tests that propagate or fail suddenly. If you see these indicators, stick to slopes less than 35 degrees and avoid traveling in or under large avalanche paths and steep slopes. Put plenty of space between where you travel and big terrain features.  

    Time and a lack of significant new stress are helping the late January weak layer. It can be found 1.5-2ft below the surface. Weak sugar-like facets (or surface hoar) sit above, and sometimes between, a crust. The weak layer is consistent on NW-NE aspects between 4,000ft and 4,700ft.  This low elevation band produced startling collapses and shooting cracks a week ago. There is uncertainty with higher elevation, alpine terrain as we have little information there. Saturday was an active day in the West North zone, where backcountry travelers triggered large persistent slab avalanches on the same layer that exists in this zone.

    A large snowmobile triggered avalanche that released on late January crust-facet layers. NE aspect at 5400' Excelsior Peak. In the West North zone. 

    Photo: Graham Clark

Avalanche Discussion

Rollerballs and loose wet avalanches (up to size D2) were reported on sunny slopes over the weekend. While wet avalanches aren't expected on Tuesday, keep an eye out for wet, weak snow. 

A week ago, signs of instability were plentiful. While you can find the weak structure and possibly concerning test results, it's now difficult to trigger an avalanche. There are signs that the weak layer is rounding and strengthening at low to mid-elevations. Information is limited above 5,600ft. Observers targeting it on northerly aspects have reported overall strengthening and decreasing likelihood of triggering avalanches. Some snow profiles and tests are still variable and indicate the potential for triggering avalanches.  After a storm brought close to 2 feet of new snow early last week, observers reported shooting cracks and whumphing collapses on northerly aspects in the low 4,000ft elevation band (top of Stevens Pass, Yodelin, and Henry Creek clearcuts) . Elsewhere, the layer combination could be problematic where you find very weak facets sandwiched between two crusts with a thin or weak upper crust.

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