Thousands of persons lined up in front of community centers and union halls again today as metropolitan Buffalo for the third chaotic day took advantage of a massive federal food-stamp giveaway.

Because of the blizzard that crippled Buffalo two weeks ago Uncles Sam is handling out millions of dollars of free food coupons in Buffalo and its wealthy suburbs. The program is a result of President Carter's declaration of Buffalo as a disaster area.

Anyone who lost any pay as a result of the blizzard that immobilized Buffalo and kept most businesses closed the entire first week of February is eligible for the food stamps. By the end of the month, more than 100,000 families are expected to have received stamps.

Blue- and white-collar workers and professional persons unable to get to their offices during the blizzard stood in line for up to six hours on Saturday, Sunday and again today.Today's lines were not as long as Saturday's or Sunday's, apparently because many had to be back at work. The program will continue daily for another two weeks, according to Erie County social services commissioner Fred J. Buscaglia.

Over the weekend, 21,300 persons who had stood in line submitted applications for the stamps, and 20,678 actually received the stamps. Buscaglia said the stamps handed out over the weekend had a value of more than $3 million. He said before the program ends he expects to process about $15 million worth.

The green Truman china, made by the American firm of Lenox, along with the Monroe vermeil flatware was chosen for the round tables seating eight or nine. The tables were covered with plain white cloths and decorated with white votive candles surrounding centerpieces of red tulips - a special Valentine's Day touch. The Carters, including Amy, were to sit at one of the round tables.

Breaking with a tradition introduced by the Kennedys, no hrd liquor was to be served before dinner. Instead the 100 dinner guests were to be offered a Washington State chablis, vermount cassis or orange juice.

The gumbo was to be accompanied by Paul Masson Rare Sherry at $4.19 a bottle; the capon by BV Pinot Chardonnay at $4.99; and the champagne for the after-dinner toasts was to be Schramsberg Blanc de Blancs at $8.99.

The 100 after-dinner guests who come in for the entertainment were to be served Taylor, Cresta Blanca and Paul Masson champagnes which cost about $4 a bottle.

Serving only American wines at White House functions is a custom which has been followed off and on since the Johnson administration, but the disappearance of liqueurs and brandies with the after-dinner coffee is a first in 31 years. According to John Picklin, he maitre d', they had been served at least since the Truman administration.

These changes in White House state dinners are very much in keeping with Mrs. Carter's descriptions of their own life style: They drink very little, they prefer hearty soups, chicken and fish rather than beef and eat very simple desserts, if any.

Haller said he likes the simplicity of the menus and believes that more than four courses is "a waste." Many American foods, he said, are appropriate for state dinners and the next one, for the Canadian Prime Minister, will be lamb or duck or beef. The President, Haller said, "loves duck."

Under the program guidelines, a family of eight would get $298 worth of stamps, a family of seven would get $262, six would get $236, five would get $198, four would get $166, three $130, two $92 and one $50 - free of charge. No matter how many members of the family might have lost pay during the blizzard, each family is entitled to only one gift.

Like Depression-era soup lines, the crowds began assembling in front of the dispensing centers four hours before the scheduled 10 a.m. opening. At one center on Sunday, those who had crowded into a doorway refused to move even to let social service clerks inside to take the applications. Instead they lifted the staff members up and passed them hand to hand over the crowd.

"We're dealing with a largely different population than we're accustomed to," said social services commissioner Buscaglia. "These are professional people and others who at least have jobs, and they're more impatient, not used to standing in line and filling out forms like our typical welfare recipient."

The neediest persons in Erie County, the estimated 100,000 elderly social Security recipients and the 50,000 chronically unemployed, are not qualified for the free food stamps because they had no jobs from which to lose income during the blizzard. Many of them are unhappy, particularly because the disaster-relife food stamps are handed out free; typically, welfare recipients pay a portion of food stamp value.