Boletín de aludes

West Slopes South

Northwest Avalanche Center
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Peligro de aludes

Wed
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The West South is on the heels of a significant atmospheric river event that brought multiple inches of rain as high as many peaks. Give the snowpack the time it needs to adjust to this gigantic load by limiting your exposure to the runouts of large avalanche paths and sticking to slopes under 35 degrees. It will take some time for temperatures to cool and the snowpack to stabilize. 

Problemas de aludes

  • Wet Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2–3

    Our concern for wet avalanches will remain on Tuesday as the West South starts to distance itself from the atmospheric river that delivered copious amounts of rain to our once dry snowpack. This water will continue to test the multiple crusts and layers of weak grains that existed in the upper snowpack prior to this event. Wet avalanches are difficult to forecast and can sometimes fail hours or even days after precipitation has stopped. Water could be pooling on one of our layers of concerns and slowly breaking the bonds that are holding snow in place. If this happens, the result could be a Wet Slab avalanche large enough to bury and kill you. In specific terrain, these avalanches could grow very large and destructive. Of course, wet loose avalanches will also be present if you venture into the mountains, and these slides could grow large or even trigger lingering slabs as they descend. Your best management tool will be to avoid the runout zone of large avalanche paths and steep slopes over 35 degrees until the snowpack has some more time to adjust to the recent load.

    (2/28/2022)

    Natural wet avalanches, including a slab and loose, were observed by patrollers at Crystal Mountain on 2/28.

    Photo: Crystal Mountain Pro Patrol

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2–3

    You could find that the very highest of elevations, such as on the volcanoes, escaped the rain and instead received multiple feet of snow. These locations may be hard to find, but if you do, tread lightly near avalanche terrain. The snowpack is certainly still in a state of transition and even if a slope has previously slid, it doesn’t mean that it can’t again. Some slopes may have gotten close to their tipping point and are just waiting for you to come along and push them over the edge. Using test slopes or hand pits probably won’t do the trick with so much snow, so you’re going to need to dig several feet down with your shovel to look at the interfaces and where instability may exist. Even still, you could have a hard time distinguishing between storm and wet slabs, or if there is a stability problem. It doesn’t really matter what you call them, your best bet is to stay on slopes under 35 degrees and give the snowpack more time to heal. 

    (1/9/2022)

    A very large avalanche from the January 6-7 cycle.  On the highest peaks or on the volcanoes, dry snow could persist and produce similar avalanches. [Pinnacle Peak NW 6200']

    Photo: NPS Rangers

Avalanche Discussion

It has been a soggy couple of days in the West South zone, and we still have one more night of rain to go. Observations and visibility have been limited around the zone, but both White Pass and Crystal Mountain Pro Patrols reported wet avalanches in the vicinity of their ski resorts on Monday. As of Monday afternoon, NWAC’s weather station at Crystal Mountain has recorded 5.75” of water since Saturday night. White Pass is approaching 3.5” of water in the same timeframe, and the expected water numbers at Paradise and Mount St. Helens should eclipse both of these. With such a wet storm, it’s not much of a stretch to conclude that a widespread natural avalanche cycle likely occurred throughout the mountains. 

We expect natural activity to taper on Tuesday, but that doesn’t mean it will be eliminated. And that doesn’t mean that the mountains won’t be dangerous. Monday night’s rain should continue to stress the snowpack. On Tuesday, slopes still may not have reached the threshold for producing an avalanche or could reach it for the second or even third time. Yes, peak hazard may have passed by daybreak, which is why we dropped the hazard level, but don’t get complacent thinking that this cycle is over. The snowpack just took on a significant load and wet avalanches are tricky, so we’re not out of the woods yet, particularly at mid to upper elevations. Although most slides likely involved the new snow that has fallen since 2/26, the possibility remains for deeper weak layers to produce very large avalanches. We wouldn’t be surprised to hear of one of these happening in the coming days, so ease back into the mountains carefully and manage terrain appropriately.  

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