February 3, 2017


Eagle River – South Fork:

Obvious signs of instability:

  • Numerous widely propagating persistent slab avalanches from Monday-Tuesday wind event
  • Numerous “whumphs” (collapses) between 2500-3000′


  • Sunny, upper elevations temps in the upper 20s to lower 30s, mid elevation temps in the teens to 20s (very inverted), calm wind

Surface conditions:

  • Variable, wind-affected snow: areas with supportable windboard, breakable windboard, and sheltered powder


Maps show widespread, natural persistent slab avalanche activity in the South Fork area from the Monday-Tuesday wind event.  Many of these avalanches propagated wide relative to their path, and all seemed to fail at ground on basal weak layers.  This is, hands-down, the most impressive avalanche cycle witnessed in South Fork in at least half a decade (this is only a partial documentation – many more aren’t flagged):

This is the avalanche (HS-N-D4-R3.5-O/G) off 4641 N aspect.  Debris pile is over 6′ tall:

This is the avalanche (HS-N-D3-R3-O/G) due E of depression 3185:

This is the avalanche (HS-N-D3.5-R4-O/G) off the ridge to the NW of 4205: