Central Sierra Nevada

Problèmes avalancheux

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1

  A wind slab avalanche problem created by snowfall and SW winds for most of the past 24 hours remains possible on NW-N-NE-E-SE aspects in near and above treeline terrain. Avalanche size up to D2 remains possible (large enough to bury or injure a person).

  The shift to light NE winds last night is expected to have had minimal scouring and redistribution effects on recently formed wind slabs. A strong N wind event forecast for this evening will create new areas of blowing snow, potentially creating additional wind slabs on E-SE aspects. Little in the way of problematic wind slab formation is expected to occur on S-SW-W aspects due to very thin snow cover. The forecast wind shift back to SW after midnight tonight will return the focus back to NW-N-NE-E-SE aspects.

  Identify and avoid areas of potentially unstable wind slab by looking for newly wind drifted snow. Slopes near or adjacent to a recent avalanche or those that have cornice features or wind pillows across the upper portion of the slope are the most suspect. Fragile cornices were reported yesterday and can collapse easily under the weight of a person. Areas of snow surface cracking in near treeline and above treeline terrain are an additional indication of unstable snow.

• 

  Wet Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1

  Small loose dry avalanches remain a possibility in steep wind protected areas below treeline where storm slabs did not form. This is most likely to occur in areas with significant previous snow cover, mainly NW-N-NE-E aspects.

  Consider how terrain may increase the consequences of a small loose dry avalanche. Being pushed into a terrain trap or over a cliff could greatly change the outcome from what might otherwise be a small inconsequential avalanche.

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Unlikely

  Taille

  1

  Storm slabs are an unlikely avalanche problem today but may occur in isolated wind protected areas below treeline on NW-N-NE-E aspect terrain. Snowpack failure would occur either within the new snow or at the old/new snow interface in most locations. Snowpack failure could potentially occur a few inches below the old/new snow interface on faceted snow in the Carson Pass area or in other areas without recent field observations. Avalanche size is most likely D1 with the isolated possibility of an avalanche up to size D2 (large enough to bury or injure a person).

  Avoid steep terrain in below treeline areas where any signs of instability have been observed. Human triggered snow surface cracking and/or recent avalanches are the easiest to identify signs of unstable snow.