let us know if you figure something out. snow always finds a place to stick
interesting to see the rear derailer wasn't too bad in this pic. but like others said, in the thick of it, you slow down & don't shift as much
my recollection of a rear derailer freezing was many years ago, the cable is what froze actually cuz the night before I cleaned the bike with some water & left it out over night. had to disassemble the cable in the dark, on my way to work, clean out the ice & reassemble. fortunately it didn't need any adjustments
how long do you think your rides will be? an hour? two? will you store your bike inside?