Observations
Front Range: Rabbit Creek
Route:
- Skinned up Peak 3 gully and over to top of Peak 3.5 along ridge at 4000′ elevation band.
Obvious signs of instability (red flags):
- Active wind loading from northerly winds observed early in the day from town (primarily appeared to be loading SW aspects). Active wind loading by 7pm on S aspects. Avalanche from a few days ago below cliff band above Hidden Lake (SW aspect Hidden Peak – see map and photos below) visible from our location. This avalanche was first reported to the AAC on 2/28/17. Suspected natural trigger from recent northerly winds loading this SW aspect, or possibly from a human snowmobile trigger. Likely HS-D2.5-R3.
Weather:
- Clear, temps in upper single digits, wind started out light from the North and picked up to 15 mph by 7pm.
Surface conditions:
- Variable: wind deposited snow over hard, supportable windboard. On S and E aspects: 1/8″ sun crust was present above ~3000′.
Snowpack:
We dug one pit in the Peak 3.5 gully (yellow diamond on map). Elevation ~4000′. HS 85cm. West aspect. 27 degree slope. Pit location was near ridgetop. See pit profile below. Results: ECTP14 SP down 35cm on laid-over buried surface hoar. Also ECTP24 SC down 70cm in the middle of the basal weak layer (advanced facets/depth hoar).
Depth hoar/advanced facet (such grains comprise the basal weak layer responsible for lower failure in snowpit test and are widespread throughout Chugach State Park at the base of the snowpack near the ground – creating a very low probability, but very high consequence persistent slab avalanche problem):
Consistent layer of soft wind transported snow below ridgeline on leeward aspects sitting on supportable wind slab:
Hidden Lake-Peak avalanche:
Map (snowpit location: yellow diamond, Hidden Lake-Peak avalanche: red outline):
