Observation: Hidden Canyon

Observation Date
12/5/2018
Observer Name
Chris Cline
Region
Salt Lake » Big Cottonwood Canyon » Hidden Canyon
Location Name or Route
Brighton- Hidden Canyon
Red Flags
Red Flags
Collapsing
Poor Snowpack Structure
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Increasing Danger
Problem #1 Comments
Dug a pit at the top of a NE facing slope along the Hidden Canyon ridgeline at about 9500 ft. About 30" of snow present. About 3-4" of surface hoar (temperature gradient) crystals, with a pretty solid 8-10" slab on top of that. Notable that the slab is also starting to get transformed by temperature gradient-- the bottom of the slab, adjacent to the TG layer, was also starting to get pretty loose, but the slab on top was pretty solid. About 10-14" of new snow on top of that-- faint layer in the middle indicating that it came down in multiple storm pulses. Snow was "finger" hard through the top layer, good settling but no slabbiness, then "fist" hard in the slab, then of course completely loose down to the ground. Shovel shear test failed decisively on the slab. With no new snow in the forecast, expect TG transformation of this relatively thin layer to continue. A good wind slab on top of the consolidating top layer should produce a classic step-down avalanche.
As an indication of the tenderness of this layer, we heard/felt collapsing at multiple places on the tour, including low angle locations amid aspen trees.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
Considerable