Central Sierra Nevada

Avalanche problems

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1

  Warmer daytime highs and strong April sun will quickly melt through last night's refreeze leaving wet unconsolidated snow sitting on top of rain crusts. Once this wet snow forms, loose wet avalanches will be possible on any steep slopes where wet snow exists. The E-SE-S-SW-W aspects that receive the most direct sunshine and low elevation northerly aspects hold the best potential for the largest wet snow instabilities, but wet snow could form on all aspects and at most elevations today. These loose wet avalanches could entrain all of the new snow and could have serious consequences for people recreating in the backcountry. While loose wet avalanches should comprise most of the wet snow instabilities, some isolated wet slab avalanches are not impossible on some sun-exposed slopes. 

  Avoid slopes where signs of rapid warming like sticky wet surface snow, roller balls, pinwheels, or other signs of wet snow exist. Once the sun hits the slopes today, the snow will quickly become unstable and less fun to recreate on and human-triggered wet snow instabilities will become possible if people venture onto slopes where wet snow exists. Seek out shaded, sheltered slopes where the snow remains cold and non-wind-affected or start and finish early before the snow warms up for better and safer recreation. 

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1

  In many areas, the wind slabs that formed during the storm should have become more difficult to trigger; however, human-triggered wind slab avalanches may still remain possible in some places. The most fragile lingering wind slabs will exist in couloirs, in gullies, on unsupported slopes, or in other complex or extreme terrain. Today's sunshine and warming temperatures could also weaken the wind slabs and cornices on sun-exposed slopes and make them more fragile and easier to trigger as the day warms up. Wind slabs could exist on wind-loaded N-NE-E aspects as well as on cross-loaded NW and SE aspects. Any wind slab avalanches that occur today could involve enough snow to bury or injure a person.

  Clues like cornices above slopes, drifted snow, ripples in the snow surface, and other wind created textures can help identify where fragile wind slabs may exist. Use this information to avoid the wind slabs and to find sheltered non-wind-affected snow to travel on.