This from the NYC DOT website:
Starting 12:01 am Saturday September 7 until 6 am Monday September 9 the Brooklyn Bridge will be closed to inbound/westbound traffic. Motorists proceeding inbound/northbound from south Brooklyn via the Belt Parkway and Gowanus Expressway should use 3rd Avenue/Hamilton Avenue into the toll facility Hugh L. Carey (formerly Brooklyn Battery) Tunnel as the best route into lower Manhattan. Motorists proceeding inbound/westbound from Queens/Long Island should consider the Williamsburg Bridge, or the toll facilities at the Robert F Kennedy Bridge or Queens Midtown Tunnel, for best route into Manhattan. Throughout this closure the Manhattan Bridge will accommodate 5 lanes of traffic inbound/westbound and two lanes outbound/eastbound.
A portion of the northbound (Queens bound) Brooklyn-Queens Expressway immediately north of Brooklyn Heights will also be closed during the wee morning hours this weekend:
The northbound Brooklyn Queens Expressway will be closed at Cadman Plaza West during limited overnight hours of 1 am to 6 am Saturday September 7th, 2 am to 7 am Sunday September 8th, and 12:01 am to 4 am Monday September 9th, 2013. Motorists proceeding toward Queens should plan alternate routes or follow posted detours at the Atlantic Avenue exit, and consider the Brooklyn Battery/Hugh L. Carey Tunnel (toll facility) for best access to Manhattan. Additionally the Hamilton Avenue entrances to northbound BQE and the Atlantic Avenue entrance to northbound BQE will be closed during hours noted above. Motorists should follow posted detours. These closures are required to facilitate NYCDOT work associated with the Brooklyn Bridge.