Mount Shasta

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–3

  West/southwest wind will be active today. Wind over the past 24 hours has blow predominantly out of the WSW, averaging 22 mi/hr with gusts to 67 mi/hr near treeline. Yesterday, wind was calm below treeline, but visible and audible above the tree tops. Plenty of low density snow remains available for wind transport. Expect cross loaded north and south aspects and leeward east aspects.Wind transports snow from the upwind sides of terrain features and deposits it into thicker drifts on the downwind side. This forms slabs in somewhat predictable and specific locations, such as below the leeward side of ridges or in cross loaded gullies. Wind Slabs can range from soft to hard, thin to thick, and are often smooth, rounded, and sometimes sound hollow. Blowing snow and cracking or collapsing in drifted snow are clear warning signs of the problem.  Wind Slabs can be avoided by sticking to sheltered or wind-scoured areas.

   

  

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–1.5

  These avalanches typically occur within layers of soft snow near the surface of the snowpack.  Dry Loose avalanches start at a point and entrain more snow as they fan out and move downhill. They vary in size, depending on how much snow is entrained and on the size of the terrain feature where they occur. Dry Loose avalanches can act as a trigger for slab avalanches. Dry Loose avalanches are the simplest problem to manage because of their predictable behavior and relatively smaller sizes. They are most hazardous if you are caught and carried into a terrain trap such as a gully, cliff, couloir, or thick trees.  Management strategies include sluff management and/or choosing less consequential terrain when this problem develops, commonly with new snow or weakening surface snow.

  

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  Depending on the storm characteristics and snowfall amounts, this problem can vary from a thin, relatively harmless soft slab to a much thicker, harder, and more dangerous slab. Storm Slab problems typically last between a few hours and a few days and are commonly distributed widely across terrain that received similar snowfall amounts. To assess potential size, monitor storm totals and expect deeper accumulations at higher elevations and in leeward terrain.  Look for feedback, such as shooting cracks, on small, steep test slopes.  Shallow Storm Slabs are most dangerous on larger terrain features or slopes with terrain traps, such as trees, gullies, and cliffs.  You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain.