Central Sierra Nevada

Problèmes avalancheux

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1.5–2.5

  We're in the realm of low likelihood, high consequence avalanches. Areas where the snowpack remains unstable are isolated. Due to this isolated distribution, the vast majority of backcountry travelers will not encounter areas of unstable snow today.

  If you do wander into an area of where instability remains, you might trigger snowpack collapse, whumpfing, or a large avalanche with no preceding signs of instability. Keep in mind that triggering a collapse is nearly the same as triggering an avalanche. The difference being that the slope was either not steep enough or the slab was sufficiently anchored to not avalanche at the time. This was the case on Wednesday when an experienced party reported triggering several large, loud collapses between 8,300’ and 9,400’ while ascending NE to ENE aspect terrain in the North Fork Galena Creek drainage, NV.

  There remains a low likelihood of triggering a persistent slab avalanche in isolated areas. NW-N-NE aspects, especially in areas where a shallower snowpack exists (think northeastern, eastern, and southern portions of the forecast area) are the areas of greatest concern. Most people will not see signs of unstable snow today. That makes triggering one of these avalanches an unexpected event for most groups. Since one of these avalanches will probably be surprisingly large, choosing simpler terrain and wide safety margins may help reduce the consequences. Lower-angle terrain options on shaded slopes or choosing alternative aspects could help avoid the problem all together.