Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Fri
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3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

A storm favoring the eastern slopes of the Cascades will bring snow, wind, and dangerous avalanche conditions in alpine terrain. You can easily trigger avalanches in freshly wind-drifted snow near ridgelines. Steer around steep slopes where you find pillow-like drifts of snow. If the sun breaks out in the afternoon, wet snow avalanches may be possible on sunny slopes.

Problemi valanghivi

  • Wind Slabs

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    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Another storm is already moving into the Southern Cascades and will likely favor the east slopes, and snow accumulations of 8-10 inches overnight are possible. Moderate winds associated with this storm will likely form fresh, sensitive wind slabs near ridges on lee aspects. With minimal direct observations, there is significant uncertainty about what types of surfaces these wind slabs will form over. After a cold, clear night on Tuesday, there is potential for slabs to form over weaker surfaces or slick melt-freeze crusts. Use visual clues like blowing snow, textured surfaces, or cornices to help you identify and avoid freshly wind-loaded slopes. You can also use quick hand pits to feel for stiffer snow layers over softer layers in wind-affected terrain. In alpine terrain, avoid steep slopes near ridges, and at lower elevations, consider low angle slopes or wind-sheltered locations. If you see signs of instability such as shooting cracks or feel the snowpack collapse beneath you, move to more conservative terrain with slope angles less than 35 degrees. You may find small storm slabs even in wind-sheltered locations if snow accumulates on weak surfaces or slick crusts. If you find more than 6 inches of new snow, use hand pits and test slopes to observe how the snow reacts before committing to steep terrain. 

    Example of wind scouring snow from windward slopes (the other side of the ridge) and transporting it onto leeward slopes.

Avalanche Discussion

Recent April storms are favoring the eastern slopes of the Cascades, and another round of snow is likely in store for the East South zone. After a stormy night, moderate snowfall will taper to showers, and there is a possibility of sun breaks in the afternoon. The strength of the spring sun can make wet loose avalanches possible even with short sun breaks, and fresh dry snow is particularly susceptible to warming and sun exposure. So if you find yourself on slopes in direct sun with snow surfaces becoming moist or rollerballs forming, it will be best to move to lower angle or shady terrain. Even a small wet loose avalanche could be consequential if it knocks you off your feet and carries you into trees, rocks, over cliffs, or buries you in confined terrain.These weather patterns are tricky to forecast, creating increased uncertainty in the weather forecasts and the avalanche forecasts. It is not unusual for spring weather to be challenging, and you should plan for some of this uncertainty when you head out into the mountains. Keep your senses tuned into the snow and look for signs of deteriorating snow stability such as recent avalanches, wet snow surfaces, actively blowing snow, or heavy snowfall.Access into areas of the East South with a consistent snowpack has become challenging, and therefore direct observations from the zone are limited. However, snow is piling up on more recent melt-freeze crusts from 4/18, and the 4/8 Crust is now 2-4 feet deep. Make snowpack observations as you travel and if you find conditions you did not anticipate, make conservative terrain choices. Some southern slopes that were recently snow-free up to 5700ft may now have over a foot of snow. Use extra caution in these lower elevations where obstacles may be lurking just under the new snow, and creek holes may be drifted over or hidden.

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