A quick query of KMFL soundings since 1995 shows that this is actually the first sub-zero 850-hPa temp in more than a decade with the previous 850-hPa temp < 0C occuring in 2010.
— Philippe Papin (@pppapin) February 2, 2021
It's only happened twice in more than 25 years! pic.twitter.com/5j74rTK9KI