Central Sierra Nevada

Problèmes avalancheux

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Likely

  Taille

  1–2

  Wind slab avalanches have continued to be reactive throughout this storm cycle with additional human triggered wind slab avalanches reported yesterday.  Strong to gale force SW/W winds yesterday and overnight built out additional dense wind slabs.  As the winds shift to the NW today and then to the N tonight, new wind slab development will be possible on any aspect in near and above treeline areas.

  Look for recent wind slab avalanches, blowing snow, new cornice formation, and dense wind pillows as clues to where wind slabs may exist.  Make a travel plan to avoid these leeward slopes near ridges and open areas exposed to blowing snow.  Cornices have become built out and large and will remain fragile again today.   

  

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1–2

  Storm snow over the past 4 days has been slow to bond and gain strength within the storm snow and at the old snow/new snow interface.  Temperatures have increased throughout this series of storms making for an upside down storm snow layer, with heavier denser snow on top of lighter less dense snow.  Multiple avalanches have occurred during this storm cycle, with yesterday being the first day without a storm slab avalanche reported.  At least some of these avalanches had graupel as the weak layer, and that may be slowing down the bonding process.  Although temperatures are expected to remain cool today, areas that receive full sun with intense solar radiation could see avalanches involving part or all of the recent storm snow as the bonds deteriorate.  

  Recent storm slab avalanches, shooting cracks, or dense snow over lighter snow, could all be signs of storm slab instabilities.  Remember, this problem will be in steep below and near treeline areas.  Be aware of terrain traps such as trees, rocks, cliffs, anything that would increase the consequences of being caught in an avalanche.  If signs of instabilities are encountered, step back to below 30 degree terrain.   

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1–2

  As our days continue to get longer and sun angles increase, solar radiation has a bigger impact on our snowpack.  With periods of full sun expected in at least some parts of the forecast area today, loose wet avalanches will become possible.  Most loose wet activity expected will be in the form of roller balls and pin wheels on wind protected E-SE-S-SW-W aspects.  Although some larger loose wet avalanches are possible that involve part or all of the recent storm snow, especially in areas that see full sun for the day.  Areas around rocks, cliffs, gully features, and any areas that are wind protected that will absorb more solar radiation will be likely areas for this problem to occur.