With all planned demolition and maintenance work completed, California Department of Transportation Officials say they will begin removing cones from the bridge and approaches around 7 p.m.
The first vehicles are expected to cross the bridge around 8 p.m., Caltrans spokesman Bart Ney said.
Motorists passing through the toll plaza are asked to drive carefully, since the merge will be different. While 20 lanes will still merge down to 5, they will curve slightly to the south, Ney said.
California Highway Patrol officers will escort the first drivers across and drivers are reminded to follow their lead and use patience when crossing the bridge tonight.
"Don't drive past any CHP vehicles unless told to do so, don't enter into any coned off areas," said CHP spokesman Officer Sam Morgan.
The bridge was not scheduled to reopen until Tuesday at 5 a.m., but Ney said unexpectedly good weather had allowed work to progress quickly.
"The next time we plan to close the Bay Bridge will be to open the new Bay Bridge, Labor Day weekend 2013," Ney said.
The bridge's upper deck was closed at 8 p.m. Friday to accommodate demolition and maintenance projects related to the construction of a new eastern span. Crews demolished sections fo roadway to make way for an inclined section that will eventually carry eastbound traffic.
The closure has pushed a surge of southbound traffic on to the Golden Gate Bridge.
Unofficial numbers show that more than 67,600 vehicles drove south over the bridge on Saturday, up from 39,799 vehicles on the Saturday of Presidents Day in 2011, Golden Gate Transportation District spokeswoman Mary Currie said.