Boletín de aludes

Stevens Pass

Northwest Avalanche Center
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Peligro de aludes

Thu
Alta montaña
1 · Débil
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

Wednesday should be a damp and mild day, with windy conditions at higher elevations. Light rain could make for easily triggered rollerballs and small wet loose avalanches on slopes that previously held dry snow. Use normal caution, exposing only one person at a time to avalanche terrain. 

Problemas de aludes

  • Loose Wet

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

    Light snow turning to rain may moisten previously dry snow surfaces. Moist, sticky snow over dry snow may create potential for wet loose avalanches on sheltered and shaded slopes. In many areas, there may not be much loose, dry snow available for entrainment, and we're only expecting very light rain.

    If you observe steady rain or wet, gloppy snow and rollerballs, expect you could initiate wet loose avalanches on very steep slopes. Keep in mind overhead hazards or other areas where getting caught in even a small, wet avalanche may hold increased consequences. 

  • Persistent Slabs

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

    Time, warm temperatures, and a lack of significant new stress are decreasing chances to trigger a persistent slab avalanche. A previously problematic layer can be found 1.5-2ft below the surface. Weak sugar-like facets (or surface hoar) sit above, and sometimes between, a crust and was buried by a storm in late January. The weak layer has been consistently found 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, alpine terrain as we have minimal information from there. Backcountry travelers unintentionally triggered avalanches on similar layers in the West North zone, and East North zone last weekend. 

    You probably won't get whumphing collapses, shooting cracks, or snowpack tests that fail suddenly. If you do see experience these signs, heed what the snow is telling you and stick to slopes less than 35 degrees. Use normal caution and avoid exposing more than one person to avalanche terrain at a time.

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

    Photo: Graham Clark

Avalanche Discussion

Very light rain may contribute to the potential for rollerballs and small wet loose avalanches on Wednesday. Looking ahead, very warm temperatures and sun are in the forecast. We're likely to experience a few days with little to no refreeze of the upper snowpack later in the week. Danger of wet loose avalanches may increase with this forecasted warm up, but there's uncertainty to how the snow may react. Rollerballs and loose wet avalanches (up to size D2) were reported on sunny slopes over the weekend. 

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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