Central Sierra Nevada

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Unlikely

  Size

  1

  Strong winds over the past 48 hours first from the SW and then from the NE have scoured and drifted snow into lee areas on a variety of aspects near and above treeline. Shallow hard wind slabs are interspersed within areas of wind scoured slopes. Recently formed wind slabs have been very difficult to trigger over the past two days. The isolated wind slab avalanche at size D1 is the lingering concern.

  Identify the smoother looking, possibly tiger striped slopes where recently formed wind slabs exist. Assess the terrain and determine how rocks, trees, cliffs, or terrain traps below could create injury or burial from what would otherwise be a small inconsequential avalanche. If a wind slab is present and the terrain below looks unforgiving, choose another slope to work with. Keep in mind that with isolated instability, everything seems stable right up until the moment that it is not. Resist lazy brain complacency.

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Unlikely

  Size

  1

  Warming air temperatures and decreased winds today will allow for minor amounts of surface wet snow formation and loose wet avalanche problems. For today, expect this problem to occur near rocks and cliffs on SE-S-SW aspects. This is where the greatest amount of incoming solar radiation and snow surface heating will occur. Rollerballs are an indication that instability associated with loose wet avalanches is forming. Avalanche size for today is expected at D1 so consequences would come from things like cliffs or terrain traps below. This avalanche problem is expected to become more likely and widespread over the next two days as the warming trend continues.