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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In sintesi

Even warmer temperatures and sunny skies will make wet avalanches the most apparent problem on Thursday. However, you could still trigger lingering pockets of wind-drifted snow at upper elevations. Steer around steep slopes with stiff wind-textured snow, and consider shadier slopes or lower angles if you begin to sink deeply into wet, heavy snow. 

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Thursday will be the warmest day yet this week. Lower elevations have surface crusts from recent warming and sunshine, so wet avalanche activity could be delayed until these crusts break down. Upper elevations and shadier aspects could start shedding wet snow earlier in the day, particularly on sunny slopes. Wet avalanches could run naturally off steep rocks and cliffs in the sun, so be aware of the terrain above you. You could also trigger these slow-moving but heavy avalanches in steep terrain. It may take some time for surface crusts to break down, but if you begin to sink deeply into wet, sloppy snow, consider moving to lower-angle slopes or sticking to more northerly aspects. 

    (1/28/2024)

    Example of small wet loose avalanches shedding off cliffs in the sun.

    S Fork Monatash Creek. 

    Photo: Katie Warren

  • Wind Slabs

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

    In some areas, stiff wind slabs formed over weak snow layers that take longer to strengthen, and you could still trigger a large, hard slab avalanche. These are becoming less likely with time, warmer daily temperatures, and cool nights. But we aren't quite ready to trust these buried weak layers. 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 drifts around rocks or vegetation and textured surfaces to help you identify likely spots for wind slabs. Be suspect of terrain features, 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 might be a lovely day in the mountains on Thursday, with the potential for sunny skies and mild temperatures. This change in weather will also bring some overlapping avalanche concerns. We have limited observations and quite a lot of uncertainty surrounding potentially buried persistent weak layers, the extent of surface crusts, or fresh snow throughout the zone. Make observations as you travel, paying close attention to surface conditions. Stiff wind-textured surfaces can point you to potential wind slab locations, and wet snow surfaces indicate wet loose avalanches are possible. You can also use quick hand pits to feel for stiff over soft snow and observe the bond with underlying crusts. When in doubt, reduce your uncertainty by choosing lower-angle terrain. 

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. We have reports of avalanches on all aspects between 5000ft and 8000ft. It has been a few days since the last reported avalanche, but these problems can be tricky and linger in certain spots like steep, rocky terrain with a shallower snowpack.  So consider reducing your uncertainty by avoiding steep, unsupported, wind-loaded terrain.

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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