Several temporary shifts in traffic on the 14th Street bridge are scheduled this weekend, according to District officials, as the city prepares to reopen the southbound span of the heavily used Potomac River crossing.

Two lanes of the southbound span, known as the George Mason Bridge, are scheduled to be reopened this afternoon, officials said. The span's two other lanes are expected to reopen between Sunday and Tuesday morning.

The span, which is normally used by nearly 90,000 cars a day, has been closed since July for extensive repairs. Officials said the overhaul was completed about five weeks sooner than predicted.

Starting early this morning, Virginia-bound traffic will be restricted to two left lanes of the bridge's middle span, known as the Center Highway Bridge. Ramps from the middle span to National Airport, the George Washington Parkway and Boundary Channel Drive will temporarily be closed.

These restrictions are designed to allow work crews to remove temporary ramps and realign traffic barriers, officials said.

Officials urged drivers heading from the District to National Airport either to use another Potomac bridge or to cross the 14th Street bridge onto Shirley Highway (I-395) and turn off at the Crystal City exit.

Starting this afternoon, the Center Highway Bridge will be closed to allow workers to shift traffic barriers and revise lane stripes. The two right lanes of the George Mason span will be open to southbound traffic.

The Center Highway Bridge, normally used by car pools, is to reopen by Tuesday, officials said.

The overhaul of the southbound span included resurfacing and widening the roadway to provide shoulders, officials said. Sidewalks were widened and new safety railings were installed between the walks and the roadway.

The repairs previously were estimated to cost $5.9 million, but officials said the final price has not been determined. Under the city's contract, A.A. Beiro Construction Co. is entitled to a $12,500-a-day bonus for completing the work ahead of schedule, officials said.