Most federal and District of Columbia workers have been given today off as officials struggled to cope with massive transportation problems caused by the worst snowstorm in two years, the crash of a jetliner into the 14th Street Bridge and a Metro train derailment.

The series of disasters locked tens of thousands of commuters in a monumental traffic jam yesterday afternoon and into the night. Scores of drivers, confused and frustrated that their normal routes home were blocked and bridges snarled with traffic, simply walked away from their cars. Many motorists waited in bars and checked into Washington hotels.

The transportation problems were expected to continue today, with more snow possible around daybreak, prompting President Reagan and D.C. Mayor Marion Barry to allow paid administrative leave for all "nonessential" employes who work in the metropolitan area. Government officials explained that "nonessential" means all those not necessary for the protection of life or national security and advised those with any doubts to contact their supervisors, who would make the determination.

"We're desperate to move people; if we can keep some people home it will help us," said Seward Cross, traffic engineer for the D.C. Department of Transportation.

The 14th Street Bridge, the major traffic artery into the city from Virginia, will be closed today while officials continue their investigation, salvage and damage assessment efforts in the wake of the airplane crash. Inbound traffic on I395 will be funneled over Memorial Bridge.

At the same time, there will be a disruption on Metro's Orange and Blue subway lines between National Airport and New Carrollton because of the rail accident.

Metro officials explained that the Blue and Orange lines, which carry traffic into the city from Virginia, will terminate at McPherson Square. The same lines bringing passengers into the District from New Carrolton and Addison Road in suburban Maryland, will end at the Federal Center Southwest station. Buses will be used to ferry passengers between McPherson Square and Federal Center Southwest while crews work on the damage to the line near the Smithsonian station.

Metro officials said that bus service is expected to operate normally, including rush-hour express service from Virginia, which will be routed over other bridges.

Because of the continued bad weather, District of Columbia, Fairfax and Montgomery county schools will be closed today. Officials for other school systems said they would decide this morning whether to open.

The George Washington Parkway, which was partially closed after the crash, is to be open today, U.S. Park Police said last night. National Airport, which closed after yesterday's crash, was to be reopened by 7 this morning, federal officials said.

Road crews struggled last night and this morning to clear streets blanketed with up to six inches of snow. National Weather Service forecasters said late last night that the area could receive as much as four more inches of snow beginning around daybreak.

The strength of the storm caught forecasters by surprise, forcing periodic amendments to their predictions as the snow continued to fall. The confusion made matters all the worse for commuters, many of whom were released from work at 2 p.m. in order to make their way home through the storm.

Within an hour, all major downtown streets were experiencing gridlock, a condition in which nothing moves.

When the Air Florida airliner struck the 14th Street Bridge about 4 p.m., many Northern Virginia commuters, who had hoped to inch their way to the suburbs, became confused as to what bridge they should take and left their cars on the streets. "If nobody tells you anything and you're stopped for an hour and a half, it happens," said D.C. Transportation Direction Tom Downs.

At the same time, rail traffic was blocked on Metro's Orange and Blue lines when a train derailed between the Smithsonian and Federal Triangle stations.

Metro officials said they were caught by surprise by the early release of government workers and were unable to round up the necessary 1,000 bus drivers to handle the early rush hour.

In addition, Downs said huge tie-ups had already been created at the 14th Street Bridge and Chain Bridge because city officials were unable to immediately reverse traffic signals and barriers for the reversible rush-hour lanes on the bridges. Virginia road crews, meanwhile, could not get their vehicles onto the streets because of the traffic jams.

With few buses in sight, some commuters took to the streets, planning to walk home to nearby residences, while others made plans to spend the night in the city. Police said they were powerless to clear the traffic.

"People panic," said Capt. Wayne Layfield, chief of the D.C. police traffic division. He said the simultaneous release of downtown workers and the frantic driving style of some area motorists in snowstorms left police with "not much we can do." Pedestrians directed traffic at some of the choked intersections.

Area hotels, which usually have plenty of rooms to rent during January, were swamped with telephone calls from people stranded in the District.

"It's unbelievable," said Mame Reiley, an assistant manager at the Watergate Hotel. At 5:45 p.m. the hotel had 45 empty rooms, and by 6:30 they had all been filled, she said. "We're asking people to double up. Our phones haven't stopped ringing," she said.

Charles Glover, who works at the Georgetown Holiday Inn, said the hotel had 300 reservations by 6 p.m., double the normal amount of business.

Those commuters who managed to leave the city did so slowly. "We've gone 70 feet in the last 20 minutes -- that's about two bus lengths," said Charles Bures, a Metro bus driver who had been heading to Virginia but was stuck in traffic at the intersection of Constitution Avenue and 14th Street at 7 p.m. He said it had taken him two hours to get from Union Station to that point.

Peter Miller, who works at The National Geographic at 16th and M streets NW, said last night that he left work at 4 o'clock, and got home to Reston -- normally a 45-minute trip -- at 7:15 p.m., and then only by a circuitous route north of the city over the Cabin John Bridge.

"It took a half an hour to go a block in town," he said. "Buses were getting stuck across intersections, and people in cars were having snowball fights with pedestrians. In most cases the pedestrians were moving faster than the cars."

Other Virginia commuters, who lived in Arlington and Alexandria, had equal difficulty. Arlington Boulevard (U.S. Rte. 50) was described at 6 p.m. by Virginia Highway official Jay Lawson as "one big parking lot -- people might as well camp overnight."

"The interstate's a mess," said Jeff Newman, an employe of Rafters Restaurant at the Landmark Shopping Center, adjacent to Interstate Rte. 395. He said frustrated motorists were filing into the restaurant. Proprietors of bars in the area also reported that business last night was up.

Schools were closed all day yesterday in at least 11 Maryland counties, including Montgomery, Prince George's and Anne Arundel. Throughout Virginia, many of the schools that did open closed early, but Fairfax, Arlington and Alexandria schools managed to stay open the whole day. The District's 90,000 public school pupils were dismissed an hour early in a fruitless attempt to avoid rush-hour snarls.

National Airport, where light morning flurries turned into a wet, clinging mess by noon, was forced to close its main 6,870-foot runway for more than an hour in the early afternoon before the Air Florida crash. After the airliner tragedy, National was closed to all air traffic for the remainder of the day and night. Dulles and Baltimore-Washington airports operated normally throughout the day and evening.