Observation: Alta Periphery

Observation Date
12/16/2021
Observer Name
Nate Hough-Snee
Region
Salt Lake » Little Cottonwood Canyon » Alta Periphery
Location Name or Route
Alta 8670' N
Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Collapsing
Poor Snowpack Structure
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
The early December facets are roughly 100-110cm under the 20211208 and 20211214 storms in upper Little Cottonwood Canyon near Alta. These facets are well-developed, relatively large, and overlay (and underlay) a partly decomposing crust. The above crust facet layer was reactive in multiple pit tests. More importantly, several avalanches were observed on this layer around Big Cottonwood/Park City Ridgeline yesterday (20211215) at shallower snowpack locations. This persistent weak layer is widespread around the central Wasatch based on my travel this week before and after the Tuesday night storm. When life throws PWLs this widespread and reactive at me, I manage my party's terrain like my life depends on it, staying vigilant and entrenched until evidence proves otherwise.
Avalanche Problem #2
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #2 Comments
Plenty of low-densty snow available for transport as next system moves through with higher winds this afternoon. Boot pen was nearly bottomless at the observation location BTL.
Snow Profile
Aspect
North
Elevation
8,600'
Comments
Pit taken as part of AAI Pro I exam; Snowpack representative of similar N-facing terrain at this elevation around Alta. Locations shows poor structure over the facet-crust-facet laye that preceded the 2021128 and 20211218 storms. Seems like a classic considerable setup with possibility of danger increasing to high with incoming winds and snow testing the PWL.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
High
Coordinates