I had to park my truck in a parking garage for three days. Lots of snow and subsequent melting appear to have leached some crud from the garage ceiling onto the truck. I'm guessing this is some sort of calcium-based crud. It's not bird poop, or else the pteranodon is breeding in Philly.

What's best to gently remove this stuff, without too much damage to the wax and clearcoat? Vinegar and water, maybe? TIA.