The Metro transit system's operations collapsed yesterday under the weight of nearly two feet of snow.

The entire 39-mile subway system was shut down as crews used plows and shovels to clear drifts from above-ground track and worked to free frozen switches. Other crews broke ice from Metro cars and towed in trains that had been caught in the open overnight.

Metro tried to field much of its normal Saturday bus service, but had to call everything back as bus after bus fell victim to snow and traffic jams. By early afternoon a few buses were venturing out; meanwhile tow trucks brought in those buses that had been stranded in Friday's massive storm.

At 8 p.m. yesterday, all Metro bus service was canceled.

Metro officials said that they hope to restore full Sunday rail service today from 10 a.m. until 6 p.m., but added that there may be no service on the Red Line between Union Station and Silver Spring. Buses will attempt to operate on a Sunday schedule, although trips will be canceled wherever roads continue to be impassable, officials said.

Full rail service is expected on Monday, they said. Full bus service also is planned, although officials said that some side streets still may be unplowed, making it impossible for buses to pass.

Officials maintained yesterday that Metro employes had made extraordinary efforts to keep the trains and buses running, but simply were overwhelmed by the elements.

"We tried to run as many buses as we possibly could to get all those people home on Friday and that's the reason why our buses are stuck on the road all over," said bus director Shirley DeLibero. At 5 p.m. yesterday, 26 buses still were stranded.

DeLibero said that uncleared roads, some blocked by stalled cars, were the chief cause of canceled service, and not mechanical failure in the buses themselves. She said that many buses may have damaged their transmissions while trying to keep driving through Friday's fierce weather.

Metro mechanic's helper Tom Kest, tending a bus immobilized by snow at 39th Street and Windham Place NW yesterday, said that buses have the same problems that automobiles encounter in bad weather.

"Every time you accelerate," he said, "it's like a light car. It starts to fishtail."

After a blizzard in 1979 during the George Washington's Day weekend shut down Metrorail service, the transit agency spent large amounts of money on new snow removal equipment. But yesterday, despite the overtime efforts of Metro employes, the equipment did not succeed.

Metro operations chief Theodore Weigle said that when snow falls at the rate the snow fell on Friday it is impossible to clear outdoor tracks without shutting down passenger service. Metro had tried unsuccessfully to keep the tracks clear of snow by running trains as frequently as possible, he said.

Metro closed its surface rail segments in mid-afternoon Friday and shut down its entire rail system shortly after 8 p.m. The system remained closed yesterday because running passenger trains would complicate the job of recovering stranded trains, servicing them, and clearing the track, Weigle said.

In addition, he said, the regulations require that all passengers trains undergo a daily safety inspection. This is done at maintenance yards, some of which remained closed yesterday.

"I am not going to operate cars without going through that safety test," Weigle said.

Three trains were stranded Friday with passengers aboard, after snow building up over the third rail broke the electrical contact that transfers power from the rail to a car's "shoe." Snow on the main tracks was not a serious problem.

Yesterday, after turning off third-rail power on surface lines, crews ran diesel engines behind plows to clear the snow from the main tracks. Then they moved in on foot to brush snow from the third rail, sometimes coating the rail with antifreeze.

Then they ran trains over the tracks to ensure that the electrical contacts had been restored, and ran the trains back and forth several times to clear any remaining snow.

By yesterday evening, crews had finished plowing the tracks between New Carrollton and the portal near the Stadium-Armory stop, where the line goes underground. The track between Rosslyn and National Airport also was cleared, and work on the Red Line between Union Station and Silver Spring reportedly was progressing slowly.

At the nine Metro garages, mechanics and drivers worked overtime to recover buses, plow parking lots, and repair buses that had suffered mechanical breakdowns in Friday's storm. Mechanic's helper Kest slept for only three hours yesterday morning in a bus in the Western garage in Friendship Heights, before returning to duty.

Metro had hoped to run nearly a full Saturday bus schedule yesterday, as well as special service parallel to the closed rail routes. But many streets proved to be impassable in both the District and the suburbs.

"Everything that we were releasing from the garages would go a few feet and would be stuck again," DeLibero said.

As a result, all service was canceled in the morning, but about 45 buses began running again such major arteries in the District as16th Street and Georgia Avenue after 2 p.m. The Bladensburg garage, Metro's largest, normally puts about 200 buses on the street on Saturdays. Yesterday afternoon, however, it sent out only 10 buses.