Thousands of Vietnam veterans, many wearing their olive green field jackets and camouflage hats, continued to descend on Washington yesterday from across the country in preparation for today's parade and dedication of the Vietnam veterans memorial on the mall.

Organizers of the events said yesterday they hope at least 250,000 veterans will be on hand for today's events, although forecasts of scattered morning showers and wind gusts that could reach 30 miles an hour threatened to dampen some of the ceremony capping the week-long national tribute.

The veterans will march along Constitution Avenue in four groups, followed by military bands and a half dozen floats, with helicopters and jets flying overhead at noon, weather permitting.

The procession, beginning at 10 a.m. at Seventh Street and Constitution Avenue, is scheduled to end three hours later at Constitution Gardens. At 2:30, the memorial honoring the 2.2 million men and women who served in the war and inscribed with the names of the 57,939 who died or are missing in action, will be dedicated.

For those veterans already here, yesterday was a day for reunions, parties and personal memorials of family and friends. Many of the veterans proudly wore the T-shirts, patches and medallions of the units in which they served.

One group that gathered for a reunion at the Capital Hilton Hotel included 48 ex-Army and Marine troopers from South Boston who in September 1981 erected their own war memorial listing the names of 25 dead from their area.

Tom Lyons, a former 3rd Division U.S. Marine who chaired the committee to erect the South Boston memorial, said he is trying to "put Vietnam behind me. I'm trying to represent the Vietnam veteran as he should be -- a John Doe average American guy who served his country."

At the Sheraton Washington Hotel on Connecticut Avenue, veterans packed the lobby lounges and bars, backslapping, drinking beer, posing for television cameras and trading war stories.

From the exhibit hall below came the electrified sounds of Ross Scarvelli and the American Dream, a Cleveland band entertaining the crowds with the songs of the 1960s -- "Abraham, Martin and John," "He Ain't Heavy, He's My Brother," "Let's Get Together" and others.

Meanwhile, organizers of the weeks' events were busy peddling $10 copies of the official "Vietnam Memorial Directory of Names," a thick, green-covered souvenir book of the names on the memorial.

Bob Janazzi, an army corporal in 1966 now unemployed in New York, said, "There are a lot of parties going on -- I'm looking for one tonight. This is really pretty good, getting the vets together. Guys are just partying, and if they happen to find someone they served with, hell, let 'em get rowdy."

Across town in Southwest, in the lobby auditorium of the Hubert H. Humphrey Building, there was a more somber gathering.

It was a reception for relatives of those killed in Vietnam sponsored by the American Gold Star Mothers, a nationwide organization of those who lost relatives in the war.

Hundreds of people, including veterans in red T-shirts, packed into the auditorium, which was decorated with military colors and gold ribbons.

"I've adopted all the Vietnam veterans as my sons," said Helen V. Stuber, national president of the Gold Star Mothers. "I invited all of my sons here. They're wearing the red shirts. I told them that to get in the door, they have to kiss their mother. I got a lot of kisses."