Boletín de aludes

West Slopes South

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

Lo esencial

Warm and wet weather will make its way toward the West South zone on Tuesday. This unusually warm storm could produce some unusual avalanches, so make sure you have travel plans with plenty of options available. Locally higher avalanche danger is expected near Paradise where the storm will be more pronounced.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    We have been dealing with Wind Slabs for a few days now and gusty winds could thicken existing or create new slabs above the rain/snow line on Tuesday. Wind Slabs like to form on the leeward side of ridgelines or near rocky features such as the base of cliffs or confined chutes. You can look for textured snow surfaces or actively blowing snow to help you identify wind-loaded terrain to avoid. Firm snow that feels hollow and breaks off in blocks is an easy indication of wind-loaded terrain and you should avoid similar snow on steeper features. Take the time to dig to see how any new storm snow is bonding to the old surfaces and for the existence of heavy snow over weaker snow. This can help you determine if slab avalanche potential is more widespread. If you suspect a slope to be wind-loaded or see shooting cracks in the surface snow, seek out simpler wind-sheltered terrain. 

    (1/9/2022)

    Visual clues such as textured surfaces and fresh cornices can help you identify wind-loaded areas to avoid. 

    Photo: Andy Harrington

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Below the rain/snow line, we’ll be dealing with wet avalanche problems. Recent snow at the lowest elevations has already been rained on and could be well suited to handle more. But rising freezing levels throughout the day means that some elevations will be seeing rain on the recent storm snow for the first time. Therefore we expect larger and potentially more widespread wet problems as you ascend in elevation. Regardless of aspect or elevation, anywhere you find rain falling on dry snow you should have these slides on your mind for slopes over 35 degrees. Wet Loose avalanches often start at a point and can entrain significant snow or even trigger slabs as they fan out and descend downhill. Your best bet will be to head for low-angled slopes away from overhead hazards such as open avalanche paths or hanging blocks of snow and ice. 

    (1/9/2022) During the storm warming temperatures and rain produced a wet loose avalanche cycle and created rain tunnels on the snow surface near and west of the Cascade crest, like you can see here on Sprial Butte, White Pass, WA. Photo: Katie Warren

Avalanche Discussion

The incoming storm is forecast to focus mainly to the north of the West South zone during the daylight hours on Tuesday. The outlier is, of course, Paradise where more precipitation is predicted and the danger should be more in line with Considerable. Generally speaking, we still don’t know a lot about conditions since the last storm but believe that the snowpack should be well suited to handle the amount of precipitation forecast for the majority of the zone. The question marks will be the increasing temperatures throughout the day and the potential for very large avalanches. The recent very large avalanches documented during our brief weather window between storms should be at the forefront of your mind heading into this storm. These avalanches occurred across the zone with very large slides documented at Mount St. Helens, Crystal, White Pass, and Mount Rainier National Park. There may be slopes that didn’t fail during the previous storm that reach their tipping point this time around. Cornices were documented to be large and primed to fail on Sunday and may release due to rain or warming temperatures. Cornice avalanches are dangerous enough on their own but could be the trigger needed to activate some of these deeper layers to produce very large avalanches. Consider limiting your exposure to open alpine terrain or large avalanche paths for the duration of this storm. 

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