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Observation: White Pine

Observation Date
12/20/2022
Observer Name
R. Kosinski
Region
Salt Lake » Little Cottonwood Canyon » White Pine
Location Name or Route
Upper White Pine
Red Flags
Red Flags
Wind Loading
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Decreasing Danger
Problem #1 Comments
The PWL is getting more stubborn as it is compressed and insulated by our last 3 weeks of snowfall. Based on what I've seen the last week, at high elevations it is becoming less likely to trigger this layer but I think it could still be activated in repeater paths, around rock bands, and in areas where the snowpack is shallower and weaker.
Avalanche Problem #2
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #2 Comments
By the time I was heading down, the winds were moderate, gusting strong, and moderate snow transport was occuring. There were isolated wind slabs but generally a wind zipper crust in most places. Winds were not transporting snow in sheltered terrain.
Comments
Started my tour around 0930 from White Pine under overcast skies and temps around 30°. The front of the storm seemed to roll in around 1130 as the winds began to pick up and by 1230 winds were moderate, gusting strong at times, generally from the south.
I dug a pit in the Rock and Roll runout zone, in a spot I know is favored for snow and has not avalanched. Total depth was 255cm and the pit showed modest rounding in the PWL from November. I think we will begin to see more rounding and bridging in this layer over the next few weeks as it is buried under ~100cm of snow. I would caution extrapolating this data to other areas of the Cottonwood Canyons as this is a favored zone that is deeper than many areas. It also appears that the windstorm that follow our November drought period destroyed the surface hoar that was 155cm above ground and left dirt in this layer. I would doubt the same is true in sheltered terrain where this layer is likely present and possibly active. at 175cm above ground there is a notable weak layer from graupel that came at the beginning of one of the December storms. It may be that there was some graupel pooling in this spot. We haven't seen any failures on this layer but it was the weakest and most identifyable layer in this pit.
The story of the next few weeks will be what happens with the PWL. In favored areas, it is likely to continue to round and bridge but in areas with less snow (lower elevation, extreme terrain, paths that have already slid) I would hesitate to think that rounding is also occuring. The PWL will continue to be a problem requiring careful evaluation for the next couple weeks.
Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Considerable
Coordinates