Thousands of people jammed Pennsylvania Avenue outside the Old Post Office Building last night to watch a massive "Love" stamp signal the start of the new year.

Attracted by unseasonably warm temperatures in the mid-40s and big-name entertainment, including Motown's Four Tops, the crowd roared with approval as the giant postage stamp likeness was lowered from the 13-story clock and bell tower at the last second of 1984 and illuminated with splashes of bright colors.

The Four Tops led a loud rendition of Auld Lang Syne while scattered fireworks burst in the air and thousands of revelers raised their arms and swayed to the music.

Wearing party hats, blowing noisemakers and drinking spirits of all kinds, the partyers climbed atop trucks, lamp posts and portable toilets for a vantage point from which to view the celebration. Music blared in the surrounding streets and echoed off the balconies within the Romanesque structure as Washington area residents of all ages thronged to Washington's newest mass meeting place.

Shortly before midnight, Mayor Marion Barry led a cheering crowd inside the Pavilion restaurant and shopping complex in a repeated cry of " '85 Comes Alive."

"I think it's great," said City Council Chairman David Clarke who was at the Post Office celebrating with his family. "We're going to compete with New York in this area, as well as others," referring to the Big Apple's famed New Year's festival in Times Square.

The crowd began gathering as early as 6 p.m., and as midnight approached, it swelled to gigantic proportions, spilling over into adjacent streets where police had sealed off traffic for a block in each direction. It was feared that an earlier threat of rain might force many to stay at home, but police estimated the crowd at some 65,000.

Last night's nonstop merrymaking, aided by unseasonably mild temperatures, was a welcoming antidote for a city still suffering the blues over the season-ending loss Sunday of Washington's beloved Redskins.

"It won't be as good as last year, when everybody was singing 'Hail to the Redskins,' " said Rick Henry, a 20-year-old student who arrived at the giant public party with two friends from Warrenton, Va. "But we're going to show our support anyway. It's going to be fantastic."

Like many others, Henry and his friends brought their own cooler of beer and other refreshments for the party around the outside stage, where the entertainment ranged from a breakdancing group called The Mighty Poppolots to the Slickee Boys, a local band, teen-age D.C. singer Stacy Lattisaw and comedienne Sylvia Traymore.

Many in the crowd took advantage of the area's expanded Metrorail system to attend the festivities from outlying suburbs.

"I have no idea what I'm doing here," said Margaret Voigt, a Commerce Department accounting technician from Washington Grove, Md. "I just love to watch people."

A threatening drizzle, which ended by evening, didn't seem to daunt the revelers, some of whom came dressed for the occasion.

Paul Downs, a 24-year-old University of Maryland student, wore a black chimney sweep costume and top hat, his body wrapped in gold Christmas garland and red satin ornaments.

"My brother was a Santa Claus this Christmas and he wanted a helper," Downs said.

Inside the building's $10 million Pavilion shopping and restaurant complex, hundreds more people celebrated in more sedate surroundings.

Dancers, some of them dressed in evening gowns or black tuxedos, glided across a ballroom floor under the structure's vaulted atrium to the swing sounds of the Mike Crotty Orchestra.

City officials had handed out free passes to the indoor festivities, and by late evening there was a crushing line at the door to get inside. Officials reported that tickets were being sold outside.

Those who made it inside could sample what was going on outdoors. A giant screen inside the Post Offfice showed a special live broadcast of the entertainment outside.

Crowds streamed by food counters, where the resident eateries serve everything from pizza to ice cream. Diners with more elaborate tastes had reserved tables in restaurants that line the interior balconies of the building.

The celebration was first held last year when city officials and local businesses picked the $38 million renovated structure, located along Pennsylvania Avenue between 11th and 12th streets NW, as a logical gathering spot.

The inaugural party attracted an estimated 25,000 persons, and from the reactions of those who attended last night's celebration, the party at appears to be a tradition in the making.

"The city has needed something like this, besides sitting home and watching New Year's in New York all the time," said Stanley Randolph, a psychiatrist's assistant at the Psychiatric Institute of Washington, who watched the dance floor action with his wife Valerie from a table in the ballroom.

"It's great to have something that brings the city together."