Observation: Mill D North

Observation Date
12/17/2021
Observer Name
E. Murray
Region
Salt Lake » Big Cottonwood Canyon » Mill D North
Location Name or Route
Mill D north to PC ridge
Red Flags
Red Flags
Recent Avalanches
Wind Loading
Cracking
Collapsing
Poor Snowpack Structure
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
November drought
Avalanche Problem #2
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #2 Comments
Winds out of the west picked up remarkably by 9 am and we're transporting the new snow which was very light in density. Rate of snow fall at this time was pretty low about S-1
Comments
Went for a walk up mill d north towards sheep shit ridge and the PC ridgeline. As we got to the top of sheep shit we noticed a large natural avalanche about 500 feet wide that had occurred overnight. We continued up the ridge towards the PC ridge when we heard a loud audible collapse. At first we couldn't tell if we remotely triggered a slide but as we continued up the ridge noticed fresh debris that continued almost all the way up to the PC ridge. Wind loading tipped the scale and added to much weight for the November drought facets to support. The slab that released was nearly a hard slab at 4 fingers plus in hardness and 2 to 4 feet deep propagating about a quarter mile up the ridge. With a little more wind loading and settlement we will have a pretty dangerous hard slab on the north half of the compass with a lot of connectivity.
After skiing terrain bellow 30 degrees we decided to dig a pit for fun and got a result of ECTP13 failing on a facet crust combo 40 cm from the ground. This test was done in a sheltered area North facing at 9000 feet.
The map below shows the general crown location of the natural in green and the remote skier trigger in red.
Today's Observed Danger Rating
High
Tomorrows Estimated Danger Rating
None
Coordinates