Observation: Mill Hollow

Observation Date
2/21/2024
Observer Name
Staples & Gile
Region
Uintas » Mill Hollow
Location Name or Route
Mill Hollow to Duchesne Ridge
Weather
Weather Comments
Weather bounced back and forth between heavy snow and sunshine
Snow Characteristics
Snow Characteristics Comments
Warm dense powder
Red Flags
Red Flags
Recent Avalanches
Cracking
Red Flags Comments
2 avalanches and shooting cracks
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
Facets on top of an ice crust about 1-2 feet deep. Mostly on sunny aspects where radiation recrystallization formed the thin layer of facets above the crust that was buried the night before Valentine's Day.
A layer of Surface hoar (frozen dew or frost) is buried on northerly facing slopes about 3 feet deep. I have been finding this everywhere I dig.
Avalanche Problem #2
Problem
Cornice
Trend
Same
Problem #2 Comments
They have steadily gotten bigger from sustained south winds. Don't get too close to them.
Comments
The Uintas don't have avalanches ripping out everywhere as in mid January, but there are definitely a few weak layers that worry me.
We looked at the recent remotely triggered slide and then triggered another both on east facing slopes near treeline. These broke on a layer of facets above a crust. I think this layer got enough warmth and sun last Saturday and Monday that it's not an issue on due south facing slopes. Certainly it's an issue on East and West and likely Southeast and Southwest.
Then we looked for a west facing slope but ended up on a NW facing slope where I didn't think we'd find a reactive Valentines weak layer. What was surprising was to find the facets without an ice crust that both produced unstable test results (ECTP10) and produced a shooting crack (photo below).
And again, as in every northerly facing pit, I found a buried layer of surface hoar with some of the largest crystals I've seen yet. (Photo below).
Video
Finally we had a close call with cornices. We triggered a massive cornice fall...like the size of a school bus. We thought we were far enough away because we didn't realize how big they were. They broke right at our skis. Clearly we were right on the line, and we were on the right side of it, but we had no margin for error and I'd say we just got lucky.
Video
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
Considerable
Coordinates