About 100,000 New Year's Eve revelers are expected downtown Tuesday night to celebrate the world's most predictable process: the passing of time.

This is the third year for the city-sponsored New Year's Eve party at the Old Post Office Pavilion. And for this year's gala, dubbed "Putting on the Glitz in 1986," the festivities stretch up Pennsylvania Avenue, to The Shops at National Place, for a simultaneous party.

The evening's entertainment is free, but entry to the shows in the Pavilion and The Shops is limited to ticket holders. Brian Tate of the Mayor's Committee to Promote Washington, chief sponsor for the event, reported that on Christmas Eve, 1,000 passes for the Pavilion, and 1,500 for The Shops were distributed through TICKETplace "in about 15 minutes."

Because of "the promotion and the caliber of entertainment this year," Tate said, officials are expecting about 100,000 people to gather outside the Pavilion exceeding the crowds of 25,000 in 1983 and 65,000 in 1984.

Outside, James Brown, "Soul Brother Number 1" known for hits such as "Please, Please, Please," and "Papa's Got a Brand New Bag," will appear, along with Willie Colon, the Del Fuegos, Experience Unlimited and On Beyond Zebra.

Inside, Cab Calloway and daughter Chris will appear, along with the Dirty Dozen Brass Band, the D.C. Jazz Orchestra, the LaVerne Reed Dancers and guitarist Bill Harris.

A few seconds before midnight a countdown begins with the slow drop of an illuminated Postal Service "Love" stamp. At midnight, the Grucci Brothers' fireworks will soar over the Pavilion.

At The Shops, Richard Bray's B.B. Big Band will perform.

Some downtown streets will be closed as preparations are made for the parties. The eastbound lanes of Pennsylvania Avenue will be closed between 10th and 12th streets NW, beginning at 10 a.m. today, and will remain closed until 7 p.m. Wednesday. Eastbound Pennsylvania Avenue traffic will be detoured north on 12th Street to E Street and south on Ninth Street.

On Tuesday, both the east and westbound lanes of Pennsylvania Avenue between Ninth and 12th streets will close at 6 p.m. Tenth and 11th streets from E Street to Pennsylvania Avenue and 12th Street from E Street to Constitution Avenue will be closed. More closings are possible to accommodate crowds and the mayor's office urges motorists to avoid the area.

Metro subway trains will operate until 2 a.m. to help revelers get home from the Washington extravaganza and other parties.

For those who show up bottle-in-hand for Father Time's big event, Mother Nature will chill the champagne. Temperatures around midnight on Tuesday are expected to be in the 30s.

The city appears to be making little headway on D.C. Mayor Marion Barry's public New Year's resolution of last year that Washington's New Year's Eve party would become the most popular in the nation.

By pitting the Federal City against the Fun City, Barry challenged a national tradition. To separate New Year's Eve and Times Square in the American psyche is like removing ground-in confetti from a deep-pile shag carpet.

The Times Square celebration has become nationally known because of its long history and the annual nationwide broadcast of the New York City party and countdown.