Central Sierra Nevada

Lawinenprobleme

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  2

  Wind drifting new snow was observed forming into wind slabs yesterday in lee areas. These slabs will have increased in size last night and may now be 2 to 3+ feet thick. Dangerous, unstable slabs of wind drifted snow are expected today above treeline and near treeline mainly on wind loaded and cross loaded NW-N-NE-E-SE aspects. Avalanche size is expected at D2.

  Identify areas where wind slabs exist and avoid them. Slopes on which wind drifted snow has deposited are suspect. Identify problematic areas with pillows of newly drifted snow, slopes below cornice features and cliff bands and route find around them. Conservative terrain selection is warranted.

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1

  Rapid new snow accumulation overnight with plenty of graupel mixed in has created the possibility of storm slabs in wind protected areas near and below treeline on all aspects. Some areas of surface hoar were reported pre storm on NW-N-NE aspects and may further contribute to instability if the surface hoar survived intact to burial at the old/new snow interface. In areas where storm slabs are not present, new snow may fail as loose dry avalanches, especially if poorly bonded to sun crust at the base of the new snow. Avalanche size is expected at D1 to D2.

  Snow surface cracking created while breaking trail in wind protected areas below treeline is a sign of unstable storm slabs in the area. Use slope angle to manage areas of storm slab or loose dry instability.