Southern San Juan
SnowpackChris Bilbrey · Dec 15, 2021 · Southern San Juan
Weather
Observed heavy snowfall (S2+) during the morning with strong southwest winds that contributed to whiteout conditions at times. Snowfall intensity reduced around 11 am and more showery by Noon. Clouds came and went for the majority of the day keeping visibility into the alpine minimal. Temperatures dropped throughout our tour. Sure looks and feel more like winter now than 10 days ago.
Snowpack
New snow totals ranged from 8-10 inches in the valley bottom to around a foot at 10,000 feet and up to 17 inches at 11,000 feet. Drifting along ridgetops and on leeward sides of slopes was around two feet near treeeline. Total snow depths on southerly-facing slopes below treeline are around two feet deep and this has made for more travel options now than just 10 days ago. On an east-facing snowpit, we observed test failures below a faceted crust that formed during warmer temperatures on 12/11 to 12/13. Though we did not observe propagating failures in this pit, we suspect that slopes harboring a stiffer, wind-drifted slab might yield different results. Evidence of this assumption was seen by a large natural slide that ran on an east-southeast alpine slope traveling around 1,000 vertical feet. Above about 10,800 feet or so, we were able to probe weaker snow in the lower snowpack on north and northeast slopes. Buried weak snow is more obvious further away from ridgetops and on steeper, heavily shaded slopes. Once we got to a part of the slope to dig a pit that we felt was representative with a slab over weak snow combination, slopes angles exceeded our level of risk and we backed off. We did not observe cracking or collapsing, but lingering weak snow below a 2 to 4 foot thick slab most likely needs more time to heal.