Central Sierra Nevada

Lawinenprobleme

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–2

  On Tuesday night, a 180 degree wind shift from SW to NE occurred. This drifted and redistributed snow on the ground. The most likely place to trigger an avalanche today is in locations where a cohesive slab of locally deeper wind-drifted snow has formed. Colder than average air temperatures during wind slab formation may prolong instability. 

  Visual clues exist to identify where potentially unstable wind slabs exist. Blowing snow, cornice formations, snow drifts, and snow surface texture indicated current or past drifting snow conditions. Use these clues to identify slopes of concern near ridgetops and gully features. Move cautiously around them.

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1.5–2.5

  In specific types of terrain, weaker faceted snow lingers at the bottom of the snowpack. Over the past two days, it has become harder to trigger an avalanche on this weak layer. We need to continue to manage this avalanche problem for a few more days while we let the snowpack continue to gain strength. Keep in mind that the snowpack does not gain strength at equal speed in all locations. Any avalanches that fail near ground level will easily be large enough to bury a person, maybe even break a tree or two. Please give our current the snowpack the respect it deserves while it continues to stabilize.

  The areas with the greatest chance of a persistent slab avalanche occurring are at and below treeline across NW-N-NE aspects above 8000'-8500'.  In isolated areas, a snowpack structure conducive to this avalanche problem has also been observed above treeline or on E aspects. As this avalanche type becomes harder to trigger, don't expect to get much feedback from the snowpack in the form of collapsing or cracking as alerts to instability.

  This avalanche type can be triggered low on a slope and from low angle terrain. Move through terrain with this in mind. You can use terrain to manage/avoid this avalanche problem. The easiest way is to choose slopes less than 30 degrees in slope angle, without steeper connected terrain above or to the side. A bit more nuanced is to seek out slopes below about 8,000' where previous rain destroyed the weak layer of concern.