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Observation: Hidden Canyon

Observation Date
12/3/2022
Observer Name
J Hirshorn & J McKnight
Region
Salt Lake » Big Cottonwood Canyon » Hidden Canyon
Location Name or Route
Picnic Tree/Lane's Leap
Red Flags
Red Flags
Heavy Snowfall
Wind Loading
Poor Snowpack Structure
Avalanche Problem #1
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #1 Comments
Winds increasing from SW, therefore with the potential to create an even bigger slab with the new snow we received late this past week. Something to keep an eye on in the coming days with addition of new snow.
Avalanche Problem #2
Problem
New Snow
Trend
Increasing Danger
Problem #2 Comments
Any new snow will certainly overload the already weak PWL which currently has ~ 4 ft of trouble on top in the form of a 3 ft slab and 1 ft of new snow.
Snow Profile
Aspect
Northeast
Elevation
9,600'
Comments
Dug a pit on a N/NE facing slope right above Lane's Leap en route to Promise Land in Upper BCC at 9,610 ft. Slope angle was 30-32 degrees, temperatures were 28 degrees F with cloudy/broken skies and winds blowing strongest from S/SW. Ran a hand hardness, ECT, CT, and Shovel Shear tests. Snow depth was 170 cm, making this one of the largest November/early December snow depths I can remember. On the ECT, there was some noticeable movement on elbow tap 5 (total 15), and full propagation observed at ECT21 right above the facet layer sitting 70cm above the ground. Video shows the slab we pulled out after all ECT taps. Hand hardness test (pic attached) showed the top 30-35 cm of new snow from this past Thursday/Friday at 4F. Right below that the hard wind slab was most consistently 1F (pencil hardness at 100-115 cm above ground). And below that...some rotten facets from the Nov warming period -- yikes. On our CT, there were collapses on CT11 with a stronger collapse on CT15 at the facet/slab boundary (again, 70cm above the ground). Sugary facets from the November warming period range from 1-2mm in size. Shovel Shear yielded no signficant results (ran the test mostly for the interest of study).
BOTTOMLINE: while it was great to have a stable snowpack for November with the ability to step into bigger lines, it is now time to back off once again! In regards to recent avalanches, observations, and our pit findings, these avalanches are nothing to mess around with. The snowpack seems like it will only get weaker with cranked SW winds and new snow on the way. The wind slab is up to 4 feet in some range locations sitting atop very weak facets.
Video
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
Considerable
Coordinates