Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Unstable areas of wind drifted snow and unstable areas of surface wet snow are the main avalanche concerns for today. Move cautiously around areas where wind drifted snow has deposited into cohesive slabs near cornices and in gullies or where surface wet snow has formed in response to daytime warming.

Problemi valanghivi

  • Wind Slabs

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

    Areas of wind drifted snow that formed into cohesive wind slabs were reactive yesterday in some ridgetop areas. Several inches of unconsolidated snow was observed yesterday along the ridgetops and available for additional drifting and wind slab formation as winds increased in speed last night. Unstable wind slabs remain an concern in areas where wind drifted snow has deposited near ridgetops and in gully features mainly near treeline and above treeline on NW-N-NE-E-SE aspects.

    Blowing snow, cornices above a slope, snow drifts, and wind-created surface textures can provide clues as to the most likely locations to encounter unstable wind slabs. Recent wind slab avalanches or snow surface cracking in wind drifted snow are signs of instability. Identify the specific areas of concern for unstable wind slabs and move cautiously around them.

    (3/30/2023)

    Unstable wind slabs failing 4 to 6 inches deep with several inches of snow on the ridgetop still available for drifting. Hidden Peak, West Shore Tahoe area, CA

    Photo: SAC

  • Loose Wet

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

    While warming since the last storm has been gradual, the strong sunshine and higher amounts of incoming solar radiation this time of year are expected to make a full appearance today. Rollerballs were observed yesterday during breaks in cloud cover on SE-S aspects as snow fell off of rocks and trees. Wet loose snow surface instabilities are expected to become more widespread today mainly across E-SE-S-SW-W aspects on slopes steeper than about 35 degrees. This problem may also develop to a lesser extent on NE and NW aspects due to the higher sun angles this time of year.

    Rollerballs, pinwheels, and signs of wet loose avalanches are indications that this avalanche problem is active. Slopes with longer sections of sustained steeper slope angles have the ability to create larger wet loose avalanches as additional snow becomes entrained following the initial point release. Slope angle is key here so move to sub 35 degree angle terrain when signs of wet loose instability are present.

    (3/30/2023)

    Roller balls formed around noon in sun exposed terrain, Donner Summit, CA.

    Photo: SAC

Avalanche Discussion

  • Unstable wind slabs were observed yesterday in some ridgetop areas.
  • Several inches of unconsolidated snow were observed yesterday along the ridgetops, available for drifting as wind speeds increase.
  • Sun crusts have formed on most sun-exposed slopes across nearly all aspects.
  • Signs of persistent instability on graupel and crust layers across NW-N-NE aspects within the forecast area have become increasingly isolated and difficult to trigger. Triggering an isolated persistent slab avalanche 1.5 to 4+ feet deep in snowpack has become unlikely on a regional scale yet still not impossible.

Regioni coperte