| Trigger | Skier | Remote Trigger | No |
| Avalanche Type | Hard Slab | Aspect | Southwest |
| Elevation | 2800ft | Slope Angle | 37deg |
| Crown Depth | 3ft | Width | 900ft |
| Vertical Run | 1000ft |
Avalanche: Turnagain
Location: Cornbiscuit Avalanche Investigation
We investigated the avalanche on Cornbisuit, collecting some data to fill in the gaps. Thank you to all of the groups involved for sharing so much info already. This observation has some of the more technical information. We will be publishing a full near-miss report within the next few days. In addition to the information in this observation, we have already posted multiple observations shared by the groups involved with firsthand accounts of the details leading to and following the event.
Avalanche Details
Crown height: 2.5-4' (80-120 cm). Deeper pockets were close to 6' deep.
Average width: 900'
Vertical fall: 1000'
Weak Layer: Facets between two crusts.
Crown elevation: 2800'
Aspect: SW
Start zone slope: 37 degrees
Alpha angle: 27 degrees
HS-ASu-R3-D3-O
The avalanche failed on a fist-hard layer of facets sandwiched between two melt-freeze crusts. This would be just below the uppermost crust of the Thanksgiving crust/facet layer. The avalanche also pulled out several pockets down to the ground as it ran. We found fist-hard 2mm facets on the ground at the crown. We did a quick ECT at the crown and got an ECTPV, with the column popping right out of the pit, failing on the same layer that the avalanche failed on.
Weather
Mostly cloudy, with an inversion. Cold in the parking lot (-6F), felt like high teens to low 20's F later in the day. Not a breath of wind, increasing clouds through the day.
Snow surface
Surface hoar up to the ridge, sitting on a layer of faceting powder. Great skiing now, not going to be so great when it gets buried...
Snowpack
See details in photos and avalanche sections.
Looking up the path from the lowest point of the debris pile. Total vertical fall was roughly 1000'. 01.08.2023
Closeup of the same view from the bottom of the runout zone. 01.08.2023
Crown depth was roughly 2.5-4' on average, with deeper pockets close to 6' deep. Photo: Matti Stilta. 01.08.2023
The avalanche was triggered on the southwest face, and the fracture propagated all the way around the west face, with another large avalanche running off the north face. There were multiple cracks still visible running across the upper west face, to within 10-15' of the northwest ridge. 01.08.2023
One of multiple shooting cracks that ran from the crown on the southwest face almost all the way to the northwest ridgeline. This one was on the smaller side of some of the other cracks we saw. 01.08.2023
Estimates for each of the avalanche paths. The max runout for the avalanche on the north side is a very rough guess. 01.08.2023
Detailed snowpack information from the crown. 01.08.2023