Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Strong winds, light precipitation, and rising snow levels will increase avalanche danger by day’s end. Rain will initiate wet avalanche activity on all aspects. Stay out from under steep terrain where you observe signs of instability like rollerballs or small wet avalanches. Look for and avoid fresh slabs of wind drifted snow at higher elevations.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    The current snow surface varies greatly by aspect and elevation. Wet or moist snow, crust, and even dry powder can be found, sometimes in close proximity. But below the surface, the snowpack is dry and winter-like. There isn't that much rain in the forecast during the day, but it's good to be on guard any time rain falls on dry snow.

    Look for initial signs of a wet avalanche instability like rollerballs or snow shedding off trees and rocks. Wet loose avalanches won't be far behind. If you observe heavy rainfall then just avoid being on or under any and all steep slopes. That includes innocuous-looking gullies that funnel avalanches debris from slopes above.

    (11/26/2021)

    Example of small wet loose avalanches triggered by rain falling on a dry snowpack.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    There isn't a huge amount of snow in the forecast for Thursday, but by the end of the day, there should be enough to make small but fresh wind slabs. Areas of wind drifted snow should be easy enough to identify. Blowing and drifting snow will show which aspects are loading up. Wind slabs will have a smooth, fat, or pillow-ish look to them, often with wind scoured snow on the ridgeline above.

    You can use test slopes to figure out how deep the slabs are getting and how easy they are to trigger. Strong winds and poor visibility might convince you to avoid steep, wind loaded terrain no matter what you find.

    Use small, wind loaded slopes to look for and test wind slabs.

    Photo: Jason Speer - Baker Mountain Guides

Avalanche Discussion

Cool but spring-like conditions are coming to an end for the Cascades. The approaching weather system is warm, wet, and windy, and a big change from the dry snow and sunny interludes we have enjoyed in the last week. It's also a strange storm in that precipitation amounts vary widely across the west slopes. Some areas like the Stevens and Snoqualmie Pass will see little in the way of rain or snow. On the other hand, the volcanoes  (Baker, Rainier, and St. Helens) and other select locations could see precipitation totals of 2.5" by Friday morning.

West Central will fall somewhere in the middle with a good shot of snow and low-elevation rain by the time the storm backs off. The most important thing to remember for Thursday is that you need to monitor conditions wherever you end up going in the mountains, especially in the afternoon. Expect higher avalanche danger - and move away from avalanche terrain -  if heavy precipitation picks up earlier than forecast or if snow levels rise ahead of schedule.  

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