What do you need a jacket for? Just wear a T-shirt or something thin and long sleeved if you're worried about tearing up your arms on the slush.
Around here 50 degree days are no-shirt days.
I'm not worried about tearing up arms on slush, I'm more worried about staying dry. A longsleeve base shirt would be fine if it were water resistant, but I cant seem to find one that is.