Avalanche

Sixmile

Rob MillspaughSwan Range
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Quick report

Collapsing
isolated

I forgot what is was like to put in an honest day of breaking trail, though I did hijack a few sled tracks where I could (Thanks!):

  • 2-6 inches of new snow on yesterday's wind stiffened surfaces at all elevations 
  • This snow fell under calm winds and concealed the usual hallmarks of wind-affected snow
  • Identified hard windslabs where my skis rode on top of yesterday's snow surface (2-6 inches deep as opposed to 12  or more inches deep)
  • Aside from two collapses, slabs were unreactive in response to my stomping
  • Intentionally triggered a small windslab at upper elevation by kicking a wee cornice
  • Noticed one other small natural wind slab triggered by cornice fall
  • Large column test at 6100', E aspect yeiled unstable results with moderate force

I enjoyed safe solo skiing on low angle slopes.  

Media and Avalanche details to follow. 

Intentionally triggered a small windslab by stomping a wee cornice along a ridge at 6800'. Cracking and collapsing were mostly under foot. 2 larger collapses at mid elevation on SE aspects. Seemed like collapses were from hard wind slabs on top of less dense storm snow.

Weather

Air Temp
17
Cloud Cover
obscured
Wind Loading
none
Recent Snowfall
5-15
Snow Avail For Transport
large amounts

Intermittent S-1 and graupel. 1-2 inches fell throughout the day. Winds calm gusting to light from the SW. Arctic air and easterly winds did not arrive at this location during daylight hours.

Snowpack

  • 5-15 cm of new snow  (F) on top of yesterday's wind-stiffened surface (4F-1F). The thickest hard slabs I found were 25 cm.  All were stubborn to unreactive.  HS = 30 cm  @ 4500', 100 cm @ 6000'.  
  • Pit @ 6100' E aspect: HS = 120 cm, ECTP 19, 20 down 60 cm on rounding facets (0.5) and surface hoar (5-10). CTM17 same layer.

Avalanche

Size
D1 R2
Type
HS
Count
2
Aspect
E
Trigger
NC
Elevation
6200 ft