You can get a good view of this phenomenon (the lift one, not the lose fuel cap!) from the ground if you watch aircraft departing on a nice day with some cumulus at about 2000'. As the aircraft approaches the cloud base, but about 200 ft before it gets there, you will see 'clouds' form around the wing root and some way along the span as the decreased pressure lowers the temperature to its dewpoint.
It is the same process which causes those narrow trails of vapour from the outboard edge of the flaps on final on a murky day. This time they are vortices.