Central Sierra Nevada

Problèmes avalancheux

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1–2

  Numerous small avalanches were reported yesterday in wind loaded areas near treeline and above treeline. Those avalanches investigated failed on a density change within the storm snow. Cold air temperatures last night and this morning may have slowed the stabilization process, allowing this instability to linger today. Any periods of rapid warming that occur today could make it easier to trigger an avalanche.

  Recent avalanches, test slope failures, and snow surface cracking may indicate that unstable slabs still exist. Identify areas where recently wind drifted snow has filled in. These frequently include slopes below or adjacent to cornice features, in gullies, and on open slopes. Often the snow on the upper portions of these slopes have snow surface texture indicative of wind loading. Once these slopes of concern are identified, move around them with caution.

  

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Unlikely

  Taille

  1–1.5

  There is a quite a bit of uncertainty today for the development of a wet loose avalanche problem. While air temperatures are well below freezing this morning, they are expected to reach near to above freezing today at and below 8,000'. The April sun is strong, so any chance the sun has to warm the snow surface during breaks in cloud cover could lead to rapid warming. Increasing cloud cover this afternoon could abruptly slow down snow surface warming. How the timing of strong solar radiation and near to above freezing air temperatures overlap today will dictate whether or not this avalanche problem materializes.

  Look for signs of snow surface warming, including roller balls and increasing new snow density (new snow changing to feel heavier). Areas around exposed rocks and cliff bands tend to warm faster than surrounding areas. Keep in mind that the sun angle is now high enough to significantly impact northerly aspects. Consider moving to lower angle slopes if roller balls or pinwheels are present.