Avalanche: Brighton Hill

Observer Name
Bill Nalli
Observation Date
Tuesday, January 10, 2023
Avalanche Date
Tuesday, January 10, 2023
Region
Salt Lake » Big Cottonwood Canyon » Brighton Hill
Location Name or Route
Brighton Hill
Elevation
9,600'
Aspect
North
Slope Angle
39°
Trigger
Skier
Trigger: additional info
Intentionally Triggered
Avalanche Type
Soft Slab
Avalanche Problem
Wind Drifted Snow
Weak Layer
New Snow/Old Snow Interface
Depth
12"
Width
300'
Vertical
100'
Comments
I triggered this small D2 avalanche on the steep wind-loaded, north-facing ridge between Brighton Hill proper and 10'420. South to southeast winds were howling by mid day creating sensitive new cornices and windslabs on NW-N-NE slopes. This little test slope was easily spottable from the side and accessible from the top. As I approached the cornice, it failed triggering the slab below which propagated surprisingly 300' wide with some speed and energy. The slope was small so it ended only 100' below in the lower angle treed slope but piled up quite deep. The slope angle directly below the cornice was steep at 39-40 deg. for a short distance. I think it needed this pitch as lower angle slopes were less sensitive and more stubborn. The weak layer was a density inversion at the old snow interface about 30-40cm down. I didnt do any tests in the hangfire as most all of the slope had avalanched but Gagne has a pertinent observation on a nearby slope that highlights this same weakness.
Touchy.
Comments
View of the cornice before the avalanche from a great side bench allowed us to evaluate the size and depth of the cornice prior to exposure. Skiing was punchy but creamy and the upside-down nature of the storm slab made for challenging trailbreaking.
Coordinates