District of Columbia officials, assured that the 14th Street bridge sustained no significant damage from the airliner that swept over the top of one span Wednesday, reopened the bridge's southbound lanes yesterday afternoon and expect to open the northbound lanes by Monday morning's rush hour.

Their action came after thousands of Virginia commuters, wrestling with what one official called "the worst transportation emergency in memory," struggled into the city yesterday amid bumper-to-bumper traffic and miles-long backups that lasted nearly until noon.

The evening rush hour moved more smoothly, but commuters are still expected to encounter serious problems on Monday because the 14th Street bridge express lanes, which are on the center span, will be closed indefinitely, forcing buses and car pools to join all the other traffic creeping into the city during rush hours. Normally the express lanes carry about half the people traveling into the city over that bridge, the major artery into Washington.

"It's going to be a mess all over," said Tom Black, Metro's director of bus operations.

The weather forecast calls for light snow or flurries in the Washington area this morning, with temperatures plunging to near zero tonight as an arctic air mass moves into the region. The arctic front, similar to one that gripped the area a week ago, is expected to last at least until Monday and may cause the suspension of the airliner salvage operations in the Potomac, officials said.

Some of the equipment involved in the salvage effort is now sitting on the center span of the bridge. That span could remain closed for weeks, depending on how much the weather affects the salvage operations, according to Thomas Downs, director of the D.C. Department of Transportation.

With the bridge closed yesterday, inbound motorists tried to squeeze onto the Memorial and Theodore Roosevelt bridges, which are heavily congested in rush hours during normal times. The result was a series of logjams on the bridges' major feeder roads--Washington Boulevard, Arlington Boulevard (Rte. 50), and the George Washington Parkway--that lasted far beyond normal rush hour periods.

"It's the pits," said Jackie Endres, who was stuck on Arlington Blvd. at 10:15 a.m., an hour and a half after she had left her Annandale home. At that point she was at the Fort Myer entrance, still about a mile from any bridge.

"I've been driving for one and a half hours," moaned Overland Belcher who was blocked nearby, en route from Tysons Corner. "They all act like they don't know which way to go."

Other motorists also said the trip into town took two to three times longer than usual.

"This morning it was a mess out there," said Maj. Larry Finks, U.S. Park Police spokesman. "There was triple the number of cars going over the Memorial Bridge. The people from Rte. 1, the Shirley Highway and the Parkway had no choice but to get into the jam."

During the normal rush hour period there was a backup of about 10 miles on the southbound George Washington Parkway, Finks said. The traffic jams continued because of the volume of cars and because the federal government's liberal leave policy allowed workers to come in late, prolonging the rush hour conditions.

"A lot of people must have thought they could lay back and come on in. They found out different," Finks said.

This all occurred with only a portion of the normal number of workers coming into the city yesterday. The 35,000 D.C. government employes had the day off for Martin Luther King's birthday, and a number of federal government employes, allowed liberal leave because of the weather and transportation problems, took the day off.

For Monday, transportation officials are urging outlying Virginia drivers to use the Beltway and enter the city, after crossing the Potomac River, on the Woodrow Wilson or Cabin John bridges. The Key Bridge, if yesterday's traffic was any indicator, also may be less congested than the Memorial or Theodore Roosevelt bridges, according to Arlington police officials.

Metro rail service remained disrupted yesterday between the Federal Center Southwest and McPherson Square stations on the Blue and Orange lines, despite assurances from Metro officials Thursday that this link would be back in operation by last night's rush hour.

Marilyn Dicus, a Metro spokesman, said the delay occurred because it took longer than expected to remove the debris from the subway wreck that killed three passengers on Wednesday. She said Metro officials hope to have the full rail service in operation today. In the meantime the transit authority has been using buses to shuttle rail passengers between McPherson Square and Federal Center.

Dicus said traffic aboard the subways was lighter than normal yesterday, and that there were no major delays. Trains were generally running at 10-minute intervals along the Red Line and 12-minute intervals along the Blue and Orange lines, she said.

Metro buses from suburban areas were running late because of the traffic tieups on the bridges and the slick conditions of some roads. Most main roads were clear as highway departments worked round the clock to deal with a total of about seven inches of snow that fell in the area Wednesday and Thursday. Traffic along city streets moved well yesterday, officials said.

The loss of the 14th Street bridge, the Metro rail accident and the bad weather this week created "the worst transportation emergency in memory," according to Downs. "It just points out how fragile the transportation system is because we are a river-bound city, with a few key bridges carrying most people into the city. Severing one of those bridges and losing part of the rail line threw the system into chaos."

The 14th Street bridge is used by about 145,000 vehicles on an average weekday, almost as many as use the Key, Theodore Roosevelt and Memorial bridges combined. It is the entrance to the city for Interstate 395, the most heavily traveled road in Virginia.

Traffic moved fairly smoothly along the bridge's reopened southbound lanes yesterday evening, but was slowed somewhat by people pausing to look for signs of the airline crash. Downs said D.C. policemen are to be posted on the bridge as long as necessary to keep people from gawking. "I expect that they will naturally want to look," Downs said. "But there is nothing to see."

Downs said that because of the snows Wednesday and Thursday, his bridge inspectors were not able to get under the northbound span until yesterday. They found that while the airliner had knocked off some paint from under the bridge, the structure is sound. City work crews were to begin at 7:30 this morning replacing 75 feet of concrete barrier and adjacent guard rail, knocked off the upstream side of the northbound span by the airliner.

Downs said he expected that work to be completed today, and that the northbound lanes could be open on Sunday, but certainly on Monday.

Virginia car pool commuters who want to use express lanes along the Shirley Highway next week can do so, but inbound motorists must exit at the Pentagon and outbound cars cannot get on before the entrance located near Washington Boulevard.

All this is going to do little to ease the frustration of commuters. Bob Walker, legislative director for Rep. Morris Udall (D.-Ariz.), took one and a half hours yesterday to get to his Capitol Hill office from Old Town Alexandria, normally a half-hour trip. He did it by transferring from bus to subway several times.

"I have to go to work," he said, "but I can't afford to take this much time. I've got to look around and come up with some other way."