Central Sierra Nevada

Avalanche problems

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  Air temperatures at the mid and upper elevations were colder last night than for the past two nights. Several hours of cloud cover last night, especially along the eastern side of the forecast area may have reduced the amount of snow surface refreeze to some degree. Areas along the Sierra Crest below about 7,000' may have experienced a weak refreeze due to the combination of above freezing air temperatures at the lower elevations and some amount of cloud cover.

  Rapid warming this morning will melt through whatever surface crust formed last night. As daytime warming progresses, wet snow will become deeper and eventually unsupportable. Larger wet loose avalanches are possible today in locations where deeper wet snow develops. Continued SW winds will likely limit snow surface melt on wind exposed slopes above treeline.

  Roller balls and pinwheels are indicators that it is possible to trigger a wet loose avalanche. When the wet surface snow starts to feel deep and mushy, move to lower-angle slopes without steep sunny slopes above to avoid this avalanche problem. Seek out shaded areas or areas with more direct wind exposure if you desire a firmer, more supportable snow surface.

  

• 

  Cornices

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  Large cornices exist along ridgelines in some locations. Areas of potentially problematic, overhanging cornice are interspersed within areas where the cornices were heavily eroded by last week's NE wind event. Cornice collapses remain a concern during this first major warming event.

  Cornice collapses are difficult to pinpoint in terms of exact timing. They frequently catch backcountry travelers by surprise by breaking farther back from the edge and wider than expected. If your route takes you along a corniced ridge, keep exposed rocks or trees between you and the cornice edge. Also, be wary of traveling on slopes below cornices where large dense blocks of snow could come tumbling down from above. It's best to avoid these slopes, but if you insist on traveling below cornices, spend as little time as possible doing so.