Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wind speeds increased last night and will continue today. Strong winds have created slabs of dense windblown snow which could be unstable. Consider avoiding slopes that sound or feel hollow underfoot, have signs of instability such as snow surface cracking, or are adjacent to recent avalanches.

Problemi valanghivi

  • Wind Slabs

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

    Ridgetop winds out of the W increased in speed last night. Winds are forecast to further increase in speed and shift to the NE today. A patchwork of rough wind scoured surfaces, dense wind slab, and firm icy surfaces exist near treeline and above treeline.  Unstable wind slabs are a concern again today in near and above treeline terrain. Due to the shifting winds, unstable slabs may be encountered on any aspect.

    Snow surface cracking may occur around the edges of these slabs, especially where they are thin. Thicker unstable hard slabs may not show cracking and may allow a person to travel far out onto the slab before an avalanche occurs. Hard slabs may feel or sound hollow underfoot. Wind exposed avalanche terrain that appears more filled in, smoother, and less scoured than surrounding areas remains suspect for human triggered avalanches today.  Consider avoiding any suspect terrain. Cornices along ridgetops are very large and should be given a wide safety margin.

    (1/21/2023)

    This avalanche was not seen while in this area on Thursday. Trigger could have been riders or cornice fall. Polaris Bowl area of The Nipple, south of Carson Pass, CA

    Photo: SAC

Avalanche Discussion

  • Two new wind slab avalanches were reported yesterday that occurred on either Friday or Saturday. A wet loose avalanche was observed on Saturday. Avalanches were size D1 to D2.
  • Snowpit tests were performed on Friday and Saturday in a variety of locations around the forecast area targeting the surface hoar buried 6 to 12 inches deep by the Wednesday night snowfall. These tests in these specific locations on a confirmed surface hoar layer suggest that this layer is unreactive. It is not impossible that an isolated area remains where buried surface hoar is an unstable weak layer in the upper snowpack.
  • Unconsolidated snow surface conditions remain in wind protected areas below treeline, especially on shaded northerly aspects.
  • A new crust will have formed on the snow surface last night on slopes that were sun exposed during yesterday's warming.

Regioni coperte