Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
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

You may be able to trigger avalanches where the wind has drifted snow into stiff slabs. A dusting of new snow may hide wind textured surfaces. Instead, feel for harder snow layers over softer layers to identify wind affected terrain and steer around steep terrain where you find these stiff snow drifts. 

Problemi valanghivi

  • Wind Slabs

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

    Tuesday night brought 6-10 inches of snow to the East South zone, accompanied by very strong winds. You can likely find wind slabs on all aspects as terrain features funneled these extreme winds in all directions. Slabs may also have formed mid-slope, further from ridges, and in areas you may typically consider sheltered. New snow depths are highest in areas near the Cascades Crest, and avalanches in these areas are more likely to be large. While these slabs are likely gaining strength, it may still be possible to trigger a large avalanche in wind loaded terrain on Thursday. Avalanches may run on the recent freezing rain or sleet crust from Christmas and travel further than you may anticipate. Recent snow, winds, and slick, old snow surfaces are a perfect setup for avalanches. A dusting of new snow on Thursday may obscure wind-textured surfaces. Instead, use your probe or ski pole to feel for stiff wind-driven snow over softer snow to identify areas where wind slabs exist. Shooting cracks and hollow sounding pillows of snow are also signs of wind slabs. Steer around steep slopes or terrain features with these signs, or consider moving to more sheltered areas. 

    (12/9/2022) Example of shooting cracks in wind-driven snow.

    Photo: Matt Primomo

Avalanche Discussion

We have been on a wild weather ride for the last few days, and the powerful winds continued to complicate the snowpack. Times of rapidly changing and active weather limit our ability to gather information on a broad spatial scale throughout the area. However, the snowpack is likely very different from a week ago. Since we have limited information, we also have significant uncertainty about snowpack conditions. We suspect many areas have a widespread ice crust from the freezing rain/sleet over the Christmas weekend. This crust may never have formed at higher elevations, and you may find a melt-freeze crust from rain instead. At trailheads at the lowest elevations, the freezing rain crust may have broken down with the recent warm temps, and you may find a saturated snowpack. With this complicated snowpack setup, you may find a complex set of avalanche problems. While wind slabs are the primary concern, at higher elevations, lingering storm slab avalanches could fail on slick crusts even in sheltered locations. Use quick hand pits or inconsequential test slopes to see how well the new snow bonds with the underlying surfaces. 

Areas just west of the crest, such as Crystal Mountain, have experienced some very large wet avalanches that failed on an old layer of weak faceted snow (11/22) buried 4-5ft deep. It will take a couple of cold days for the liquid water to work its way out of the snowpack where significant rain fell on the formerly dry snowpack. While unlikely, large triggers such as a cornice fall or snowmobiles could trigger one of these avalanches. If you are traveling near the Cascade Crest and find yourself sinking deeply into wet, heavy snow or find large wet snow grains in the snowpack, there may be an increased likelihood of triggering one of these large slides. 

Travel conditions may be challenging with thick, icy crusts on many surfaces.

If you get out into the mountains, let us know what you see by submitting a public observation!

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