Central Sierra Nevada

Lawinenprobleme

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1

  Slabs of wind drifted snow and large fragile cornices exist on wind-loaded and cross-loaded NW-N-NE-E-SE aspects. Yesterday skiers triggered small wind slabs on NE and SE facing slopes. Similar human triggered wind slab avalanches remain possible. Strong winds could also add additional snow to these wind slabs today. These fresh wind slabs should remain small in most places but some of them could entrain enough snow to bury or injure a person. It is not impossible that a wind slab avalanche or large cornice failure could provide a large enough trigger to break the buried persistent weak layer mentioned below.

  Identify where wind slabs may exist using clues like cornices above a slope, drifted snow, wind-scoured ridges, and other wind created surface textures. Travel plans that give wind-loaded slopes and the cornices above them a wide berth will help avoid unexpected wind slab avalanches or cornice failures. Plenty of great snow exists on more sheltered terrain. 

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Unlikely

  Größe

  1

  No new persistent slab avalanches have been reported since Friday. Additionally, snowpit data targeting the persistent weak layer (surface hoar on top of a thin crust) shows a strengthening trend in the snowpack. Triggering a persistent slab avalanche has become unlikely on a regional scale. Unlikely does not mean impossible and some isolated terrain feature on a NW-N-NE aspect may still hold a pocket of unstable snow. In the unlikely event, someone does trigger one of these avalanches they could still break 1 to 3 ft deep and propagate around terrain features.

  Some uncertainty still surrounds this unusual problem. Continue to pay attention to where an isolated persistent slab might exist especially in terrain with the potential for larger triggers like cornice failures or wind slab failures. Digging into the snow and testing this layer can help provide information about the location and state of the weak layer. If you have any lingering doubts about the potential for a persistent slab avalanche, go ahead choose a different aspect or more conservative terrain.