had a similar issue as yours at 19K miles. mine was happening about the same speed and would get louder from a low speed to a dead stop. per the chrylser dealer i took it to, it was the supercharger bearing that went bad. chrysler dealer doesnt simply change the bearing but replace the whole s/c instead. if you have a warranty then you're in luck as you'll get a new s/c for a bad bearing.

if this will be out of pocket cost to you, you should be able to get the s/c pulley bearing replaced fairly cheap. if it's the bearings inside the s/c housing itself then you can send you're s/c to a company like psesuperchargers.com and get it remanufactured.

good luck...