Metro and District of Columbia officials were set to restore another vital link in the city's transportation system today, but because a key span on the 14th Street bridge will be closed indefinitely, officials were predicting enormous delays tomorrow morning affecting almost all of the 120,000 commuters heading into the city from Virginia.

Transportation chiefs released a temporary master plan to deal with the disruption, rerouting buses and restricting car pool access, but they still fear that commuters will face extended ordeals of bumper-to-bumper traffic.

In the wake of the most massive disruption in public transportation here in 25 years, officials urged commuters to leave for work earlier than usual tomorrow, use public transportation or car pools if possible, and to be tolerant.

"We're going to have a big traffic jam," said Thomas N. Black, chief of bus operations for Metro. "We were caught by four disasters last week, one after another. I've never seen anything like it and neither has my senior staff."

The D.C. Department of Transportation reopened the northbound span of the 14th Street bridge last night, and Metro officials said they would have the Orange and Blue line subway link between McPherson Square and Federal Center Southwest operating today. But the center span of the 14th Street bridge, which carries express lane traffic, remains closed indefinitely for the effort of salvaging the bodies and wreckage in the airliner crash.

The National Weather Service is calling for mostly sunny skies today, with temperatures between 15 and 20 degrees, following overnight temperatures that were expected to plunge to 10 degrees in the city and near zero in the suburbs.

This Arctic cold air mass is supposed to move out of the area tomorrow, with temperatures rising to near freezing. There is also the possibility of light snow tomorrow, according to the weather service. Road crews have most of the main roads cleared of the 6.4 inches of snow that fell on the area last Wednesday and another inch Thursday.

After working through much of yesterday, crews for the D.C. Department of Transportation finished repairing the concrete barrier and guardrail on the northbound 14th Street bridge, and traffic was allowed on the span at 5 p.m.

Transportation officials are concerned that traffic across the bridge will be further slowed by people pausing to look for signs of the airliner crash and salvage operation. Black noted that traffic moved at 10 mph on the newly reopened southbound lanes Friday, and at 35 to 45 mph after it was dark and impossible to see. D.C. police will be stationed on the bridge to help keep traffic moving.

Metro officials, meanwhile, said late yesterday that they planned to reopen today the rail link between McPherson Square and Federal Center Southwest that has been closed since Wednesday's subway wreck. That link was supposed to be open by Friday's rush hour, but Metro officials said it took longer than they thought to remove debris from the site. Metro spokesman Cody Pfanstiehl said rail service would certainly be in operation on Monday. Metro officials planned to discontinue the shuttle-bus run between the two subway stops after the Orange and Blue lines are fully back in service.

"We got hit with four whammies at once," said Black, in explaining the transportation emergency that officials say is the worst since public transit workers went on strike for 52 days in 1955, shutting down the system. "We've been known to handle one whammy before, but certainly not four at once."

The temporary plan put forth by transportation officials calls for the termination of most inbound Virginia bus routes at the Pentagon during the morning rush hour. From there commuters will be taken by shuttle buses across the 14th Street bridge into the District. Car pools, meanwhile, will be forced to leave the express lanes well short of the 14th Street bridge.

Black said that in spite of the delays on Friday when the morning rush hour was extended until about noon as motorists scrambled to get into the city, the system hasn't really been tested yet because many government workers were allowed last Thursday and Friday off, and others came into the city late. "Monday will be the first big test," he said.

Metro officials, in conjunction with the D.C. and Virginia transportation departments, have released the following plan for weekday public transportation and car pools while the express lanes on the 14th Street bridge remain closed:

BUSES

* Route 11 buses from Old Town, Alexandria, and Route 16A, 16D and 16E buses from Culmore in Arlington will follow normal routes over the Memorial Bridge, with significant delays expected.

* Route 5K, 5S, 38A, and 38B buses from McLean and Vienna will follow normal routes over Key Bridge, with significant delays expected.

* Route 5W and 5Z buses from Vienna and 38C buses from Ballston will follow normal routes over the Theodore Roosevelt Bridge, with significant delays expected.

* Route 16B and 16C buses from Culmore in Arlington will travel downtown via the 14th Street bridge, with significant delays expected.

* All other District of Columbia-bound buses from Virginia will terminate at the Pentagon during the morning rush hour, 6:30 to 9:30 a.m. There shuttle buses, dispatched at a supervisor's discretion, will carry passengers to terminal points at 10th Street and Pennsylvania Avenue NW or Seventh and D streets SW via the 14th Street bridge. After crossing the bridge, passengers may exit at any Metro bus stop along the way.

* Bus passengers bound for Virginia from the District during the morning rush hour must take the shuttle to the Pentagon from terminals either at 10th Street and Pennsylvania Avenue NW or at Seventh and D streets SW.

* After the morning rush hour, buses bound for Washington from Virginia, excluding any of those listed above, will operate as scheduled over the bridge normally used.

* After 9:30 a.m., Virginia-bound buses from the District will operate on the regular weekday schedule and will take the bridge normally used.

* Route 30 buses from Friendship Heights to Southern Avenue SE are expected to experience significant delays during the morning rush hour.

* Other routes in the District and Maryland are not expected to be affected.

CAR POOLS

* Inbound car pools on the Shirley Highway (I-395) must exit the express lanes at Washington Boulevard and should proceed into the District via the Memorial Bridge. Car pools headed for the Pentagon, Pentagon City or the Crystal City area should display a handwritten "P" through the front windshield and may continue past the Washington Boulevard exit on the express lanes to the Pentagon exit. Signs will be posted along Eads Street to direct drivers exiting at this point. No express-lane traffic will be permitted beyond the Pentagon exit.

* Outbound car pools should not enter the Shirley Highway express lanes until the Turkey Cock Run entrance, located about eight miles from Washington between Duke Street and Edsall Road.

* The car pool express lane on Arlington Boulevard (Rte. 50) will be in operation as usual, with possible significant delays because of heavy traffic on the Memorial and Theodore Roosevelt bridges.

On weekends, beginning today, the regular weekend bus schedule between Virginia and the District will apply, but during Metrorail operating hours--8 a.m. to midnight on Saturday, and 10 a.m. to 6 p.m. on Sunday--bus passengers between the District and Virginia must use the shuttle buses operating between the Pentagon and the terminals at 10th Street and Pennsylvania Avenue, and at Seventh and D streets, connecting to regular weekend bus service at these points.