Central Sierra Nevada

Lawinenprobleme

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  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–2

  Strong to gale force SW winds will continue through today transporting snow onto NW-N-NE-E-SE aspects in wind exposed areas.  Winds will slightly shift throughout the day to the W and eventually to the N tonight as winds start to decrease.  Wind slab avalanches are expected to occur today and could be up to size D2.  Wind slabs that receive large amounts of solar radiation may further weaken causing failure.

  Look for clues such as recent avalanche activity, blowing snow, wind pillows, and snow surface scouring to determine where these wind slabs are forming.  Make a plan to avoid steep wind loaded terrain and areas below large cornices.

  

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  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1.5–2.5

  A layer of surface hoar was buried on Sunday March 19 that was the failure layer in at least some of the avalanches reported this past Monday.  Multiple layers of graupel also exist in the upper snowpack with some still showing weakness with snowpack tests.  No avalanches have been reported since last Monday, but with continuous small storms, visibility has been limited and uncertainty continues to exist.  Additional snowfall over the last few days and today is gradually increasing the slab depth and continuing to provide stress to these weak layers.

  Recent wide propagating avalanches, unstable snowpit test results, snow surface cracking, snowpack collapse, or whumpfing are all signs of unstable snow in the area.  If signs of instability exist, move to non-avalanche terrain with no steeper connected terrain above.

  

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  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–2

  Intense solar radiation from strong March sunshine may occur today.  Depending on location, long periods of full sun could be enough to wet the snow surface and cause wet loose instabilities to form.  As the snow surface becomes wet, it's time to change aspects or move away from avalanche terrain.  Roller balls and pinwheels would be signs that the snow surface is losing strength, with larger wet loose avalanches entraining more of the recent storm snow becoming possible.