Justin Bieber performing a free concert in Rockefeller Plaza and President Obama a few blocks away at the New York Sheraton at a fund-raiser at around the same time tonight — means super-gridlock for midtown Manhattan. There will be frozen zones, roped off zones, and shoulder-to-shoulder can’t move zones. Teen idol Justin Bieber is part of the annual Rockefeller Christmas Tree Lighting ceremonies from 7 PM to 9 PM, and if his free concert last week in Rockefeller Plaza for the Toyota Today Show Concert Series is a measure, Bieber fever starts the night before, when fans start to gather. My advice — stay home and watch the show on TV. Avoid midtown tonight.