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Observation: Silver Fork

Observation Date
12/2/2022
Observer Name
Alden and Zanetti
Region
Salt Lake » Big Cottonwood Canyon » Silver Fork
Location Name or Route
Lower Silver Fork
Red Flags
Red Flags
Cracking
Collapsing
Poor Snowpack Structure
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
Various layers of faceted snow grains were observed below the new snow from the two precipitation events this week. Perhaps most concerning was not any results from our pit (although it showed a number of red flags as well) but the collapsing experience with nearly every step while skinning. While no resounding "whumphs" were heard and cracking was limited to 2-4' from loading, this is likely a function of the current strength of the slab overlying the persistent weak layer. I would assume with additional loading from wind and snow in the coming day, this slab will gain strength and become increasingly well connected between non-planar terrain features and across larger distances.
Avalanche Problem #2
Problem
Wind Drifted Snow
Trend
Decreasing Danger
Problem #2 Comments
Some patches of textured snow surface were observed although we were below treeline and cannot speak to the more significant winds at higher elevations. That said, the slab overlying the PWL with these wind deposits seemed to produce cracks roughly twice as long as areas less affected by wind.
Snow Profile
Aspect
Northwest
Elevation
8,100'
Comments
Stuck our shovels into the snow on a NW aspect at 8100' and found a number of concerning problems with the current snowpack structure The persistent weak layer is very weak (fist) and composed of large, well developed facets with some buried surface hoar at this wind sheltered location.
An Extended Column Test failed on the third tap from the wrist and collapsed roughly half the column without propagation (ECTN3 Q2 @48cm). ECTN was observed opposed to a collapse propagating across the whole column presumably due to the relatively weak (fist to 4 finger) cohesiveness of the slab (see Avalanche Problem #1 notes above). A shovel shear test produced similar results, failing with minimal pressure on the same layer of large (1-2mm), sugary facets (STE Q2 @48cm).
Video
Today's Observed Danger Rating
High
Tomorrows Estimated Danger Rating
Considerable
Coordinates