Mount Shasta

Problemi valanghivi

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Possible

  Dimensione

  1–2

  Tuesday's storm dropped about 12 inches of wet, dense snow (3.28" SWE) at the Old Ski Bowl (7,600 feet). Higher elevations probably received over two feet of drier snow. Strong southwest through northwest winds during the storm formed wind slabs in the alpine. Yesterday, northwest winds continued to blow snow across upper elevation ridgelines on Mount Shasta. This morning, these winds have increased in speed with plenty of dry snow available for transport above 9,000 feet. These new and previous wind slabs may be sensitive to the weight of a skier or rider. 

  You are most likely to encounter the problem on steep slopes (>35 degrees) on the leeward side of prominent ridgelines. Watch for blowing snow, fresh cornices, and pillow-shaped features to alert you to recently wind-drifted areas, and consider avoiding these slopes. Shooting cracks are a clear sign of unstable snow.  Stick to wind-scoured or sheltered terrain to help manage this problem.

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Unlikely

  Dimensione

  2–2.5

  While unlikely, there is a potential for large avalanches on buried graupel layers. These layers are widespread in the upper snowpack and have been found on the west and east sides of the forecast area at all elevations. Feedback on these layers has been limited in snowpack tests, but they are suspected in two large natural avalanches, including the slide observed yesterday in the Old Ski Bowl. Both avalanches released during significant storms, which rapidly loaded the snowpack. The February 14th graupel layer is buried about three feet deep near treeline on Mount Shasta and sits atop a melt-freeze crust. 

  Today's warm temperatures will continue to send meltwater through the snowpack. While very challenging to predict, the potential exists for meltwater to pool and weaken these weak layers to the point of failure. Steep, solar aspects near treeline in areas where the graupel layers have been identified - such as Power Bowl and Sun Bowl - deserve extra caution.

  Any avalanche failing on a buried graupel layer would propagate widely and be difficult to escape. Consider avoiding steep areas below cliff bands and around rocky features. These are locations where graupel may have accumulated and where the weak layers may be closer to the surface and more easily affected by the weight of skiers or riders. As always, evaluate the consequences before committing to steep terrain. Or, give the snowpack more time to adjust to its recent load, and for additional information to be gathered on the sensitivity of these layers. 

  

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Possible

  Dimensione

  1–1.5

  Snow surfaces on steep (>35 degrees), solar aspects may lose cohesion as the late-February California sun warms snow surfaces today, especially under rocky terrain features. You may also find this problem on lower elevation terrain on the north half of the compass, where snow surfaces experienced a poor refreeze last night. Even small wet loose slides can carry you into undesirable terrain like cliffs and gullies. If you observe signs that the snow surface is losing cohesion, such as fresh rollerballs, move to mellower or shadier slopes.