Bollettino valanghe

Central Cascades

Central Oregon Avalanche Center
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Pericolo valanghe

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

Triggering a slab avalanche will be likely in wind drifted snow and possible in new storm snow on Thursday. Moderate to strong southwest winds will load north and east facing lee slopes near and above treeline. Ease into steep terrain, evaluate slopes for windloading, and if you see signs of unstable snow such as cracking or previous avalanches increase your safety margin by moving to lower angle options below 30 degrees.

Problemi valanghivi

  • Wind Slabs

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

    Previously formed wind slabs will be trending toward being stubborn to trigger but a new round of snow combined with wind is expected on Thursday. New wind slabs will build throuthout the day. The extent and depth of new wind slabs will depend on how much new snow we get. Remember, wind deposited snow can be many times deeper than the snow that has dropped out of the sky.

    Wind slabs typically form below ridge tops, high points, and terrain features that catch blowing snow. 

    Watch for signs of blowing snow to indicate slopes are becoming loaded. Look for visual clues on the snow surface, such as pillowy deposits and wavy or ripply surface texture, to let you know if previous wind transport has occured. 

    As drifts become deeper, resulting avalanches can become larger. Ease into terrain by checking out the wind loading on lower angle slopes. Monitor the depth of wind slabs and look for signs of unstable snow such as cracking in the slab or recent avalanches. If you can judge that a slope has not been wind loaded, then a wind slab is not a problem.

  • Storm Slabs

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

    On Wednesday, surface snow remained cold and light where it had not been affected by the wind. On Thursday, warming temperatures and snowfall will deposit a heavier storm layer on top of recent snow. As this falls on the colder and lighter snowpack, storm slabs will build and be possible to trigger throughout the terrain where wind has not redistributed snow. Although storm slabs will not be large enough to bury a person on most slopes, watch for terrain traps such as gullies and depressions that can increase the consequence of being caught in a storm slab avalanche. 

Avalanche Discussion

The snow level is expected to rise on Thursday to around 5800 ft and we could very well see snow turn to rain at lower elevation areas like Santiam Pass. When snow turns to rain be aware of changing surface conditions; small wet loose and small wet slab avalanches will be possible as the upper snow layers become slushy and saturated. Roller balls and pinwheels are precursors to the wet type avalanches.

On Wednesday, recent storm snow was found to be 'right side up', meaning the snow becomes denser and firmer with depth. Storm slabs were found to be stubborn to non reactive.

No avalanche activity was reported on Wednesday but we have limited observations from the upper elevations.

Anytime you have doubts about the stability of the snowpack, move to lower angle slopes less than 30 degrees steep.

 

 

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