Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

Very dangerous avalanche conditions are expected near and above treeline, so avoid traveling into places where avalanches can start, run, and stop. You could trigger large and surprising avalanches in steep, open terrain where weak snow sits over a slick crust. Professionals have observed clean and planer failures in the upper snowpack, and we expect conditions to become active on these deeper layers on Friday.

Problemi valanghivi

  • Storm Slabs

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

    Significant new snowfall is expected with fluctuating temperatures and very strong wind. It doesn't take a rocket scientist to tell us that conditions will be prime for avalanches on Friday. Stay aware as you travel through snow and take notice if you see shooting cracks or recent soft avalanches. The new snow will sit over a variety of weak surfaces and older weak layers. In some areas you could produce deeper and more surprising avalanches. Strong wind will also redistribute snow in exposed terrain. For these reasons, avoid slopes that are steeper than 30 degrees.

    Example storm slab on a small test slope.

  • Persistent Slabs

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

    The new snow will stress deeper weak layers in the snowpack, and you could trigger wide and surprising avalanches. These could be 2ft+ deep and could be triggered from a distance or from below on connected slopes. Look for shooting cracks and whumphing collapses as telltale signs of instability. The problem appears to be variable throughout the mountains. Some slopes may have the ability to create these large and surprising avalanches, while other ones may not. The tricky part is that it will be very difficult to tell. When the snowpack is this complex, keep your terrain choices simple. Elevations below 4,500ft may offer significantly lower chances of triggering one of these. 

    (2/5/2021) This avalanche was remotely triggered in backcountry terrain just outside of the Crystal ski area. Similar to other recent slides, it failed on facets just above the 1/13 crust. 60cm deep, 150' wide. 5200' ESE aspect. Photo: Crystal Mt Ski Patrol

Avalanche Discussion

We are headed into another storm cycle, and this time Stevens Pass could do fairly well with new snow amounts. We don't expect the snowpack to be able to handle this storm very well, because professionals have observed sudden, planer, and often easy failures with snowpit tests in the upper pack. Others have observer spooky collapsing. Weak snow above and sometimes within the crust from January 13th is now a concern in the zone with added snow and wind loading. Until recently, there hasn't been much new snow or slab over this layer, but we expect that to change on Friday. 

Under the thicker canopy of the trees, the snow conditions may begin to improve with this storm. Previously they were variable, with icy, bumpy surfaces and plenty of downed trees and branches. 

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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