Central Sierra Nevada

Lawinenprobleme

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1.5–3

  Our recent storm ended last night with 1 to 3+ feet of new storm snow.  At the base of this storm snow exists a layer of graupel on top of a firm melt freeze crust.  Some avalanches reported during this storm cycle have failed on this graupel/crust combo, especially in wind loaded areas with a cohesive slab.  The possibility also exists that other weaknesses exist around this old surface crust with whumpfing sounds, slope scale collapses, and large shooting cracks reported through the storm cycle.

  Southwest to west winds will be strong to gale force today with large amounts of snow available for wind transport.  Wind slabs will continue to form below ridges, in gully features, and in open areas.  These wind slabs could fail down to the new snow/old snow interface resulting in large to very large avalanches 2 to 5 feet deep.  Large cornices are built out along ridges and will be fragile and could collapse today.

  In wind protected areas, storm slab weaknesses could continue with potential weak layers at the base of the snowpack.  Uncertainty exists as to how reactive these layers will be moving forward.  Limited observations and very poor visibility during the storm cycle has decreased data collection.  Avalanches that occur today in the upper snowpack, could step down to this weak layer at the old snow/new snow interface causing much larger avalanches and consequences.  Any warming today could increase the likelihood of triggering any of these storm slab issues. 

  Recent avalanches, snow surface cracking, or snowpack test failures will indicate unstable snow in your area.  Traveling on slopes that are under 30 degrees in steepness with no steeper connected terrain near or above will be the easiest way to avoid this avalanche problem.  Avoid slopes below large cornices and steep wind loaded terrain.  Plan routes to avoid you and your group's exposure to this avalanche problem.