Avalanche: Alexander Basin

Observer Name
Grainger
Observation Date
Monday, December 21, 2020
Avalanche Date
Monday, December 21, 2020
Region
Salt Lake » Mill Creek Canyon » Alexander Basin
Location Name or Route
Alexander Basin
Elevation
9,400'
Aspect
Northeast
Slope Angle
40°
Trigger
Natural
Avalanche Type
Soft Slab
Avalanche Problem
Persistent Weak Layer
Weak Layer
Facets
Depth
20"
Comments
Traveled Bowman/Yellow Jacket out Alexander Basin today to see what natural activity occurred with Thursday/Friday snow. I couldn't see prominent crowns from afar in the Porter Fork/Gobbler's NW area but walking any ridgelines that had seen last weekend's wind produced collapses and shooting cracks with almost every step (Pic 6). While many slopes under ~35 degrees had collapsed and stayed in place along the Yellow Jacket ridge, Alexander was a different story. At least two of the chutes of Depth Hoar Bowl naturaled and once debris reached more continuous terrain below the midslope rock bands, the slab propagated across the majority of the bowl's NE aspect.
Pic 1 shows a slab that initiated closer to the ridge ~35' wide and the propagation under the tree and rock bands underneath (Pic 3). Pic 2 is similar more Northerly facing in the bowl. Crowns were generally 14-20" failing on extremely weak November facets.
I triggered one more chute from the ridge, wind-affected snow collapsing and propagating to the crown ~50' downslope.
Interestingly, the East Bowl didn't have any debris or crowns visible from the ridge, possibly due to more complex terrain and rock features breaking up the facet layer. The uppermost basin of Alexander had a few smaller crowns visible midslope or lower.
Today's warm temps turned the south half of the compass moist and some wet-loose activity was present on steep SE-W slopes as well as lower slopes of all aspects.
Comments
The deer whose tracks are in Pic 5 gambled and got lucky, it appears his/her tracks fractured the slope above but the slab arrested.
Coordinates