Thousands of commuters and travelers were stymied by yesterday's sudden snowstorm, which forced the closing of National and Baltimore-Washington International airports, disrupted Amtrak service in and out of Washington's Union Station and choked most Metrobus routes for much of the day.

However, the Metrorail system, which has not received or installed most of the snow-removal equipment bought since it was knocked out by last winter's twin snowstorms, won the rematch by providing rail service all day with few delays.

The transit agency hoped to have full bus and rail services today, but a Metro spokesman said last night that a final decision was to be made at 5:30 this morning. Metro was planning to run trains through the night to prevent rails from freezing.

Scores of Metrobus routes were severely limited in the District and Maryland yesterday and, after 3:15 p.m., Metro halted all bus service in and out of Virginia except on cleared snow emergency routes, spokeswoman Beverly Silverberg said.

"It's bad, very bad," Silverberg said of bus service, attributing the problems to road conditions, including accidents, hilly terrain and the rate at which local and state governments were able to clear the snow.

That yesterday was the Veterans Day federal holiday considerably lightened the load on the local transportation system, but scattered breakdowns and other problems created crowd scenes reminiscent of last winter's snow days.

Union Station was jammed for three hours while a frozen track switch trapped four Amtrak trains waiting to depart and five trains waiting to arrive, directly affecting up to 3,000 passengers and causing delays to ripple up the heavily traveled Northeast corridor to Boston, said Amtrak spokeswoman Sue Martin. The 2 p.m. Metroliner to New York was canceled.

National Airport opened at 8 a.m., one hour late, and closed at 10:15 a.m. Spokesman David A. Hess said last night that it was hoped that regular service can be resumed at 7 a.m. today.

David Hind was trying to get to Sydney, Australia, when he was stranded. After two weeks of visiting the States, he was headed there via Chicago and Los Angeles. He got stranded around 1 p.m. "There's been very little information about what was happening and little information about the facilities available to us." Hind set up a little room with his luggage and passed the time by reading a book.

BWI closed its main runway from 2 to 3:50 p.m., said spokeswoman Linda Green. The airport's smaller runway was open during that time, but handled very few flights because of limited visibility, she said.

Dulles' main runways remained open throughout the day.

Officials at all three airports cautioned that service today would depend on the weather. "It's snowing heavily again," Green said late yesterday afternoon, "and we're still plowing."

Metro's Farragut West station, recently criticized for fencing out the homeless overnight, had to close its entrance to patrons at 2:30 p.m. because of crowds on the underground platform.

"There are trains coming, but I have no idea when they'll get here," the station attendant said, according to one frustrated commuter who gave up and left. Metro scheduled trains on a weekend schedule, with the Red Line running every 10 minutes and the Blue, Orange and Yellow lines running every 15, creating much wider gaps between trains than during a normal workday.

Last January, two heavy snowstorms in four days forced Metro to shut down the 37 outdoor miles of its 70-mile rail system after ice coated the 750-volt third rail, which powers the trains. Service was disrupted for days as the snow froze track switches, blew the fuses in the car motors and jammed countless car doors.

Metro's one disruption in rail service yesterday occurred when a track switch failed on the Yellow Line, halting service between the Eisenhower Avenue and Huntington stations from 1:15 to 2:30 p.m.

After last winter's problems, the Metro board of directors adopted a $28 million, three-year program to equip the system to run in heavy snow, and voted to spend $10.3 million of that this year.

However, most of the new equipment has not been delivered or installed, and may not be fully in place until Jan. 30, or one month later than originally scheduled, Metro officials conceded two weeks ago.

The centerpiece of the new weaponry was to be $7 million worth of electrical heating tape needed to warm the third rail to 35 degrees, which should melt snow before it ices over and disrupts power.