Observer Name
Grainger, Young, Robertson
Observation Date
Thursday, March 26, 2020
Avalanche Date
Thursday, March 26, 2020
Region
Salt Lake » Park City Ridgeline » Squaretop
Location Name or Route
Squaretop
Elevation
9,800'
Aspect
Northeast
Slope Angle
39°
Trigger
Skier
Trigger: additional info
Cornice Triggered
Avalanche Type
Soft Slab
Avalanche Problem
Wind Drifted Snow
Weak Layer
New Snow/Old Snow Interface
Depth
15"
Width
100'
Vertical
900'
Comments
The all-star skiing today yielded little in terms of slab or dry-loose instability. Issues we encountered were mainly on ridgeline slopes approaching 40 degrees that had been affeected by light (moderate gusts) SW winds over the last 2 nights.
This slab was the result of a moderate-weight cornice test on the top of Squaretop and propagated the last 2 days' new snow (15"), ~100' wide, a solid D2 result running full track to the flats.
Greenhousing Saturday through Monday provided a 1F thermal crust as the bed surface and Monday afternoon's trace of low-density snow was the failure layer with a 4F-F wind-affected slab propagating ~45' on each side of the cornice impact.
I found no Tuesday graupel in the trigger area of this slide, possibly due to steep/hard bed slope angle shedding it. This slab along the flanks failed CTV (on isolation).
This slab was isolated in its location and reactive due to slope angle. It was critical to read terrain conservatively in S and W wind-load areas today and important to find slopes in the low 30 degrees where skiing was unbelievable.
Photos-
1- Flank near the top
2- Right flank looking down, debris to near the elevation of the lower flats
3- 4F-F slab with thin weak layer on top of thermal crust
4- Humans for scale
5- Other than the Squaretop slab, instability was limited to this kind of sluffing on slopes over ~35 degrees
Coordinates