Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

The weather pattern has the avalanche conditions set to "repeat." You could trigger avalanches in wind-drifted snow at mid and upper elevations. These avalanches could be just a few inches deep in freshly wind-drifted snow or break deeper into older, stiff wind drifts 2-3 feet deep and could be large. Steer around steep slopes with stiff wind-textured snow. 

Problemi valanghivi

  • Wind Slabs

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

    Wind slabs are becoming more stubborn to trigger with time. However, in some areas, these stiff wind slabs formed over weak snow layers that take longer to strengthen, and you could still trigger a large, hard slab avalanche. A few inches of fresh snow and another day of easterly winds also means you could find shallow new drifts to trigger a small avalanche. Winds have blown in multiple directions over the last few days, so look for wind slabs on various aspects or even mid-slope. Strong winds have pressed these slabs into firmer 1F-P hard slabs in exposed alpine terrain. Consider the high consequences of triggering a wind slab that breaks wider and deeper than expected if it fails on weak snow above the Early February Crust. 

    Use visual clues such as blowing snow and textured surfaces to help you identify where the wind has been at work. Be suspect of terrain features that encourage drifting, such as the leeward sides of ridgelines, alpine couloirs, gully features, and cross-loaded depressions. Dial it back if you notice shooting cracks, whumphs, or hollow-sounding snow. 

    (2/18/2024)

    Triggering a wind slab in the wrong spot could result in a much larger and wider avalanche if it breaks on old snow above the Early February Crust. 

    Forecasters observed this 1-2 day-old avalanche in the Teanaway drainage on Sunday. 

    W aspect, 6200 ft

    Photo: Katie Warren

Avalanche Discussion

It feels like we're stuck in a Groundhog's Day repeating pattern of weather and avalanche concerns. Tuesday will bring another 1-3 inches of fresh snow and moderate Easterly winds again. With this pattern, we are incrementally loading weak snow layers both in sheltered and wind-drifted terrain, where slabs are much thicker and more dangerous. In terrain sheltered from the wind, this snow lacks the slab-like characteristics to produce an avalanche, but this is beginning to change with the continued trickle-in of snow. Anywhere you find more than 8 inches of snow above a stout crust or see wind-textured surfaces could be problematic. These slabs may not be that deep but could be large enough to ruin your day if they propagate widely on well-developed facets over a crust. 

Since February 14th, storms have brought 14-16 inches of snow to the East South zone. In much of the region, this new snow now sits over persistent weak layers of faceted snow over the slick Early February Crust (EFC). Observers in many areas of the Cascades, including in an NWAC forecaster in the Darland Mt area on Thursday, are finding this weak, faceted snow just above the stout EFC crust and also over a thin, breakable crust buried on 2/14 on southerly aspects. This persistent weak layer has already produced avalanches in neighboring zones (observation here). We have quite a lot of uncertainty with the sensitivity and distribution of this avalanche problem. But, since February 15th, 13 unintentionally human-triggered avalanches have failed on or just above the EFC throughout the Washington Cascades. Most of these avalanches have been between 5000ft and 8000ft and cover all aspects. Thankfully, no one was injured in these incidents, but this is critical information that this weak layer can still produce avalanches. It is best to stick to sheltered terrain or low-angle, well-supported slopes while the weather keeps giving us windy conditions along with dribs and drabs of snow. 

Lower elevations and southerly aspects have seen warming and sunshine. Both now have melt-freeze crusts of varying thickness on the surface. However, temperatures will notch up again on Tuesday, and you could see some wet loose avalanches or rollerballs a bit higher in the terrain than on Monday. 

Expect very thin (or even non-existent) snowpacks at lower elevations and on some steep southerly slopes. Unfortunately, we're still talking about travel hazards. Slick crusts, exposed obstacles, open creeks, and bare ground continue to make travel more adventurous. While the continued snow is a welcome refresh, it's best to use established roads and groomed trails for better access to the high country. 

Your avalanche, snowpack, or weather observations are extremely valuable to the avalanche community. Help create a more accurate avalanche forecast by submitting your observations here. 

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