Bollettino valanghe

East Slopes Central

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

Sunnier skies, along with an increase in temperatures, will make wet avalanches your primary concern on Thursday. Although, you could still find a lingering pocket of wind-drifted snow where you could also trigger an avalanche. 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 with recent dry snow. 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. 

    (12/17/2023)

    Wet loose avalanche debris off of the cliffs above. As rocks warm quickly in the sun, wet loose avalanches become more likely.  

    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, particularly in the Wenatchee Mountains, where recent observations indicate a poor bond between the recent snow and the Early February Crust. 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 quite a lot of uncertainty surrounding potentially buried persistent weak layers, the extent of surface crusts, or fresh snow throughout the zone. The bond with the stout Early February Crust (EFC) is favorable in some areas. In others, like the Wenatchee Mountains, it is a weak bond with well-developed, faceted snow above the EFC. 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. 

The Wenatchee Mountains and other drainages in the southern reaches of the zone received 10-16" of recent snow. Initially, the new snow fell very cold and low density. However, recent warm temperatures are consolidating the surface snow to form a more cohesive slab. This slab may rest over weak, faceted grains or surface hoar associated with the Early February Crust or a sun crust on southern aspects. This hasn't become a widespread problem yet, but 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. It has been a few days since the last reported avalanche. Unfortunately, these problems can be tricky and linger in certain sub-ranges like the Wenatchee Mountains or near specific terrain features like steep, rocky slopes with a shallower snowpack. So consider reducing your uncertainty by avoiding steep, unsupported, wind-loaded terrain. 

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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