Bridgeport Avalanche Center

Avalanche problems

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1–2.5

  Heavy, dense snow with high winds around the Sierra Crest will create instabilities within the new snow today. With over an inch of water overnight at our Leavitt Lake SNOTEL sensor and 1-2" of Snow Water equivalent (SWE) forecasted today into tonight, we will see a rapid amount of snow accumulate in a short amount of time. This new snow does not have enough time to bond and stick to itself which can lead to a widespread natural avalanche cycle. The new snow that falls through a storm can also experience fluctuating temperatures and changes in density causing instabilities within the new storm snow.  Wind-driven snow or wind slab snow is included in the Storm Slab label listed above. With the wind from the SW, expect northerly aspects to be loading up and releasing throughout the storm.

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1–2.5

  High-elevation rain on snow will create widespread unstable wet snow avalanches today.  The problem starts as the surface snow becomes wet and points of snow release, fan out, and entrain or gather up more snow while traveling downhill.  A slow-moving avalanche can quickly gain speed and become massive, traveling with the force of a freight train. While the problem is identified above as Wet Loose, it is also possible for slabs to break out as the entrainment process occurs. Our snowpack is highly variable with several crust and facet layers mixed throughout the upper pack. Water has a way of finding the lowest spot and that can mean traveling along crusts or percolating through crusts, saturating the upper snowpack. Sheltered areas where loose, dry surface facets exited before the rain will have more snow available for wet loose avalanches to form. Wet snow avalanches are very destructive and can often run further and longer than expected. Avalance paths that have little or no snow are still suspect today as an avalanche from the snowier upper elevations could run their full paths into lower elevation terrain.