Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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In sintesi

Don’t let the relative break in the weather fool you Sunday and lure you into steeper terrain. Several storms over the past few days created various potential weak layers in the snow. Stay off of open slopes greater than 35 degrees and give the snowpack time to adjust to the recent load.

Problemi valanghivi

  • Storm Slabs

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    The parade of winter storms across our region just keeps going, and the next big snow producer should build fresh slabs Saturday night. With high precipitation rates and relatively warm temperatures expect overnight, this storm could cause a natural avalanche cycle. Don’t be surprised if you see piles of debris or new crowns covered by a couple of inches of light dry snow Sunday. Even though we expect the bulk of the avalanche activity to occur overnight, you can still trigger these new storm slabs on open slopes greater than 35 degrees. While you’re most likely to trigger these shallow new slabs, with all the recent snow, several potential weak layers now exist in the upper snowpack. Any avalanche could break on these deeper layers or entrain significant amounts of snow resulting in large and deadly avalanches. Simple small slope tests and hand-pits may not paint a clear picture of the dangers from all these various layers. Be patient and give the snowpack time to adjust to the recent load. 

    With cooling temperatures, you may find several inches of light unconsolidated snow at the surface. This may produce loose dry avalanches in steeper and even treed terrain. While these sluffs can seem harmless, don’t let them catch you off guard and knock you into a terrain trap.

    (1/1/2021) Testing storm snow layers on a small unsupported slope at Stevens Pass.

Avalanche Discussion

Snoqualmie passed a notable milestone on Saturday. The mid-mountain weather station at Alpental broke 100” of settled snow joining the ranks of Mt Baker and Paradise to achieve this mark for the season. This is due in no small part to the ongoing storm cycle since 12/29. As of Saturday afternoon, Snoqualmie Pass received over 6” of precipitation resulting in more than 3.5 feet of snow at 4300' in the past 4 days. As snow totals continue to grow, so does our uncertainty. Several natural and triggered avalanche cycles resulted from this recent weather, and more could be on the way. If you use the break in the storms Sunday to venture into the mountains, remember, a lot has changed and the snowpack may not have fully adapted to the recent loads. 

At mid and lower elevations, a large chunk of this recent precipitation fell as rain. Even though temperatures should cool, that might not end the wet avalanche problems. Be particularly leery of slopes where you see crevasse-like glide cracks. Glide avalanches can occur days after the rain stops. 

I’d like to thank all of you for submitting your observation in 2020! As of today, we have had 92 observations from the Snoqualmie zone on our public site. Your observations help us create the best possible forecast. Keep it up in 2021!.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources. Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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