Central Sierra Nevada

Problemi valanghivi

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Possible

  Dimensione

  2–3

  Old weak faceted snow exists below multiple feet of recent storm snow in parts of the forecast region.  These weak layers recently reached their tipping point and have been slow to stabilize.  Reports of continued instability include:

  • Whumpfing sounds reported at Picketts Peak, Carson Pass area yesterday.
  • A snowmobile triggered avalanche occurred Sunday along the Forestdale Divide on a slope with numerous previous tracks on it. This was a N to NE aspect slope around 9,300'.
  • One snowboarder was caught and carried on Saturday in a wide propagating size D3 avalanche on a N to NE aspect around 9,200' near Blue Lakes, south of Carson Pass. This avalanche was triggered during the group's second run on the slope.
  • A snowboarder remotely triggered a size D2 avalanche Saturday near Ebbetts Pass on a N aspect near 9,000'.
  • Multiple other parties reported additional snowpack collapses and whumps in the Carson Pass and Ebbetts Pass areas both Saturday and Sunday.

  Large to very large human triggered avalanches remain possible on these weak layers.  Signs of instability have been mainly focused on the eastern and southern portions of the forecast region, especially in the Carson Pass to Ebbetts Pass areas.  The areas of concern are NW-N-NE-E aspects above 8000'.  The western and northern portions of the forecast area received more rain which helped to destroy and strengthen some of these weak layers or leave a strong and thick rain crust adding strength and support above these layers of concern.  Signs of instabilities have become more limited, including variable snowpack tests.  Most of the recent avalanches reported had previous tracks on the slopes prior to the avalanche occurring.  Steep complex terrain with multiple trigger points remains some of the most likely areas for these avalanches to occur.

  Conservative terrain choices and decision making are the best strategies to manage this avalanche problem if traveling in areas highlighted above.  Utilize simple terrain under 30 degrees in steepness with no other steeper slopes above or around.  Another option would be to recreate on SE-S-SW aspects where this avalanche problem does not exist.  These weak layers are expected to continue to gain strength on a day to day basis, but these gains will be different area by area.   While the chances of triggering one of these large avalanches is decreasing, it only takes one large to very large isolated avalanche to ruin your day.