Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

A recent storm and gusty winds mean you could easily trigger avalanches in wind-drifted terrain at mid and upper elevations. Some of these stiff slabs formed over weak snow and could break wider than you expect and become large. Your best option is to choose slopes sheltered from the wind or low angled terrain to enjoy the fresh snow without triggering a large and surprising avalanche. 

Problemi valanghivi

  • Wind Slabs

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

    As you gain elevation, you'll find deep drifts, especially in the southern part of the zone that received 12-14" of recent snow. These wind slabs may rest over weak, faceted surfaces or the slick Early February Crust (EFC). Avalanches could break widely and in surprising ways where they rest over these weak grains. To avoid triggering an avalanche, stick to lower angle and well-supported slopes at mid and upper elevations. The recent erratic wind patterns have distributed snow in unusual locations. Look and feel for wind-textured surfaces or pillow-like drifts to clue you into where these slabs are likely to reside. 

    The stronger mid-February sun effect may create cohesive slabs even outside of wind drifted areas. If the sun warms the southern slopes, you could begin to see avalanches in more sheltered terrain. Make frequent observations as you travel, and if you find the recent snow consolidating, consider backing off steep slopes into lower-angled terrain or shadier areas. On Friday, a skier triggered an avalanche on weak snow on a southerly aspect, and backcountry travelers in the Icicle Creek area reported large natural avalanches in wind-loaded terrain at upper elevations. We are unsure of the distribution of where these slabs rest over weak faceted snow, so keep this in mind and make more conservative decisions to account for the increased uncertainty.  

    (2/16/2024)

    A skier triggered this avalanche on Friday on a southern aspect at 5500ft in the Teanaway area. Notice the textured surface indicating wind-transported snow. 

    Photo: Max Bednarski

Avalanche Discussion

You'll likely see increasing cloud cover throughout the day on Saturday. Temperatures will remain cold, but the sun is growing stronger this time of the year, so it could start to affect snow surfaces more substantially. With the low density of the new snow, sluffs may run naturally with direct sun, or a person could trigger one on a steep slope.

The Wenatchee Mountains and other drainages in the southern reaches of the zone received 10-16" of recent snow. This fresh snow still doesn't have much cohesive slab structure in sheltered locations, and you'll likely be traveling right through the crust below. However, in many places, the fresh snow rests over weak, faceted grains or surface hoar associated with the Early February Crust (EFC) or a sun crust on southern aspects. Without a cohesive slab, this hasn't become a widespread problem yet. However, in areas where the wind drifts snow into stiffer slabs or the sun and gradually warming temperatures begin to consolidate the new snow, we'll likely start to see avalanche activity increase throughout the zone. 

On Friday, observers in the Icicle Creek area saw a few large to very large naturals in wind-loaded terrain at upper elevations. Before this last storm, two skier-triggered avalanches failed on weak, faceted snow over the EFC: A small avalanche in the Icicle Creek area and a slightly larger avalanche on Jim Hill in the Stevens Pass zone. These avalanches could be the first sign of larger and more destructive avalanches that propagate widely with additional loading or warming temperatures. On Thursday, Mission Ridge reported triggering shallow (5-8" deep) slabs that ran on the old/new interface with control work. On the same day, I was out on Blewett Pass and found that areas with wind drifting produced shooting cracks easily when provoked. I also got one collapse, and the culprit was a thin layer of faceted grains above the EFC. While my extended column test results (ECTN 7) did not show a likely chance of propagation on this layer, I suspect the overlaying slab was just not cohesive enough. Check out the full observation here.

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