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Observation: Hells Canyon

Observation Date
2/21/2023
Observer Name
Staples
Region
Ogden » Snowbasin Backcountry » Hells Canyon
Location Name or Route
Sloth Ridge - Hells Canyon
Weather
Precipitation
Heavy Snowfall
Weather Comments
Snowing hard. No wind where I was which only went up to 7600'
Snow Characteristics
New Snow Depth
6"
New Snow Density
High
Snow Surface Conditions
Powder
Snow Characteristics Comments
Dense, right side up, powder that made great skiing. About 6 inches of new snow as of 1600.
The Boardwalk station at 8000' at Basin recorded a new snow of 6.8" with a snow density of 13%
Comments
Skinned up Sloth Ridge just north of Snowbasin to assess how the new snow was bonding to the old snow surface and if there was any faceted snow underneath that has been found in other areas.
Somewhere under 7000', air temps were above freezing until about the middle of the day. These above freezing temps helped the new snow bond to the old snow quite well.
It looks like temperatures remained below freezing at all the weather stations nearby above 7000'.
Once I got to 7600', I was able to find an obvious faceted layer on a NE facing slope on the divide between Coldwater Creek and Hells Canyon. See photo of a stripe in my pit wall. It was hard to examine the crystals well under such heavy snowfall, but it appeared to be a mix of broken stellars (snowflakes), faceted broken stellars, a few random surface hoar crystals (1mm in size), and some very small faceted crystals (0.25mm). Regarless of the exact crystal form, they would readily scatter across my crystal card. This layer was about 3-4 inhces under the old snow surface. I suspect this layer formed late last week and was capped by Sunday's 2-4" of snowfall.
I did multiple extended column tests on this layer. It would only break under my shovel (ECTN) and not propagate. However, when I tapped on the remaining 60 cm of the column (the full column width of a ECT is 90 cm), it would break across the whole column after 10 taps. What does this mean? (1) At my location at that time, it wasn't too concerning, (2) It tells me that it could exist in other places and possibly be more likely to produce an avalanche, & (3) Later this week I'll be hunting for it.
However, that layer is an academic distraction for Wednesday. The weakest layer was within the new snow. It would readily shear in any type of test, formal or informal. More importantly, I was able to trigger a shallow soft slab in the new snow. It was only 5-6 inches deep and about 30 feet wide on a 40 degree rollover.
For Wednesday, the main focus will be slab avalanches of new snow and wind-drifted snow which could be widespread problems. Moving into the rest of the week, we'll have to see if more people find a buried faceted layer, and if it produces avalanches after the storm related instabilities have stabilized.
Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Considerable
Coordinates