Central Sierra Nevada

Problemi valanghivi

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Possible

  Dimensione

  1–2

  New snowfall since Friday has been heavily biased towards the eastern side of the forecast area. The avalanche problems are present in some locations within the forecast area and completely absent in others. The conditions you encounter will be highly dependent on where you choose to go within the forecast area.

  The vast majority of our snowfall events are accompanied by SW wind. This recent storm has been different, with a constant NE wind. As a result, the distribution of wind slabs is different from a typical day with new snow and SW wind. NE winds have been blowing and drifted new snow since Friday afternoon. This has filled in places on the leeward sides of ridges, in gullies, and on open slopes, creating cohesive slabs of locally deeper wind-deposited snow. These new wind slabs have formed on top of either sugary faceted snow at the old snow surface or on top of firm ice.

  Use clues such as freshly built drifts, cornices, and firm, scoured snow surfaces to identify where blowing and drifting snow has occurred. Identify the locations where blowing snow has drifted and filled in the terrain, making locally deeper areas of new snow. These are the specific locations of concern for a wind slab avalanche. Recent avalanches and cracking in the snow surface are clear signs that new wind slabs are unstable. Traveling in wind protected areas such as tree-covered slopes or places where other terrain blocks the wind can reduce the exposure to this avalanche problem.

  

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Unlikely

  Dimensione

  1–1.5

  Some small dry loose sluffs may be triggered again today by backcountry travelers in steep terrain. Anticipate this avalanche problem on any aspect in locations where at least a couple of inches of new snow has accumulated. These small dry loose avalanches could run on ice/crust, on top of soft faceted snow at the old/new snow interface, or within the new snow. For today, most of the hazard associated with this problem comes from being carried into or over down slope hazards such as rocks, trees, or cliffs rather than from burial.

  Selecting less steep terrain can be an easy way to avoid this avalanche problem. Otherwise, if opting for steep terrain, choose sections of terrain that avoid consequential down slope hazards.

  There is a small chance today that some of these dry loose sluffs could transition to wet loose avalanches on sun exposed slopes near rock outcroppings and cliff bands. In combination with the brisk NE winds, air temperatures are a little cold for this today, but wind protected areas around exposed rocks that heat up more than surrounding areas might warm enough to make the snow surface wet. Wet loose avalanches are expected to become more of an issue tomorrow as air temperatures climb above freezing in more areas and NE winds decrease.