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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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You can trigger a large avalanche in wind-drifted snow at upper elevations, and old icy surfaces still pose lingering travel hazards. Use visual clues to identify and avoid steep open slopes with evidence of fresh wind loading.

Problemi valanghivi

  • Wind Slabs

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

    SNOTELs throughout the East South Zone report 4-6in of new snow over the past 24 hours. Strong to extreme westerly winds accompanied the new snow, and will continue to blow Tuesday as this storm squeezes out an inch or two more of cold, dry snow.

    Avalanches in wind drifted snow will become larger and easier to trigger as you gain elevation. These avalanches could fail on the icy (and potentially weak) old snow surface buried January 30th, or within new and wind drifted snow. Avalanches will be easiest to trigger on east through north aspects in terrain 35 degrees and steeper. Steer around large open slopes below cornices, cliff bands, and ridgelines with evidence of fresh wind loading. Look and feel for changes in snow surface texture and hardness. You may find windward slopes scoured to the old icy surface, and leeward slopes drifted in with chalky snow. Use these visual clues along with blowing snow as the easiest tools to identify slopes with fresh wind slabs. If you experience cracking or see recent avalanches, choose lower angled terrain sheltered from the wind.

    (1/31/2022) Westerly winds blowing snow at ridgetop, scouring down to the hard, icy old snow surface and loading a NE aspect. Photo: Andrew Kiefer

Avalanche Discussion

This storm provided a much-needed refresh after a prolonged period of dry, sunny weather. With the improved riding conditions comes an uptick in avalanche danger at upper elevations, especially in areas closer to the Cascade Crest that received more snow. Carefully evaluate new and windblown snow before committing to steeper terrain. You may find fresh slabs generally 1ft thick or less, but triggering a deeper, larger wind slab is not out of the question on Tuesday.

The new/old snow interface (buried January 30) is a pronounced marker in the snowpack throughout the region, and something to track closely moving forward. Although the recent storm started warm and finished cool, new snow may take time to bond to slick and icy old snow surfaces. In some isolated areas, weak snow may exist above or below the old crust and be capable of producing surprising avalanches. The old snow surface will be easy to find, so gather information as you travel. Build in a wide margin for error and move to lower angle terrain if you experience shooting cracks, collapses, or see recent avalanches break widely across terrain features. The old snow surface may even be exposed or shallowly buried in some areas, especially in windward terrain (S and W aspects), and below treeline where less snow accumulated. In these slippery areas, anticipate lingering travel hazards.

Over the past three weeks, conditions were unseasonably warm and the snowpack endured a beating. There was a significant loss in overall snow height, and many ridgelines, south aspects, and low elevation slopes melted out to bare ground. Several creeks also reopened during the warm weather and many snow bridges fractured or collapsed. Shallowly buried obstacles will be an additional hazard to deal with in the coming days hidden beneath the new snow. 

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