Rubbing sound - Water Cause Problems?

Just started hearing a fairly quiet rubbing or grinding sound once per one of the front wheels rev. (Perhaps best described like a brake pad scraping one spot on a disc when I roll very slow.)

I cannot see or feel anything around an axle or between the tires and wheel wells.

This is rainy season in Florida, and I did go through one nasty standing water spot recently, so I imagine some shmutz could have splashed onto the brake pads.

Car is still in the warranty period, but I suspect something like "shmutzy pads" will be called "severe use".

Anyone else had this?

 

Superb - I was wondering how to do it without regen braking.