Depositors flocked to area savings and loans and banks yesterday following the announcement that interest rates on All Savers certificates will drop sharply on Monday.

The news that the rate will drop from 12.14 percent to 10.77 percent brought the biggest crowds in a month into savings institions to buy the tax-exempt certificates, but the crowds didn't match the outpouring of a month ago when sales began.

"There's an awful lot of demand," said Perpetual-American President William Sinclair yesterday afternoon. "The lines are beginning to build, and we're putting on extra help for late afternoon and Saturday," he said. "I think the writing is on the wall now, and they're going to run on in during these two days."

Several institutions plan to be open today for customers who want to snatch up certificates before the rates decline.

"The change, as substantial as it is, has caused larger-than-normal activity, but it doesn't match the volume we had when the certificates first came out," said Stephen Detwiler, senior vice president of First Federal of Arlington.

The drop in rates was announced Thursday evening on the basis of the monthly auction of one-year Treasury bills. When the All Savers certificates first went on sale in early October, the rate was 12.61 percent.

Volume in All Savers began increasing Thursday evening and continued to build yesterday. The Westover branch of First American Bank of Virginia had been handling one or two requests for All Savers certificates a week until yesterday, when the volume increased to more than 30 new accounts, a spokeswoman said.

Some decline in the rate had been expected, but the size of the decline appeared to catch banking and thrift officials by surprise.

"I think some people felt it would come down, but this is a major drop," said Michael Smith, senior vice president of Government Services Savings and Loan.

"I think it caught everybody by surprise. It caught us by surprise," said Howard Millner, senior vice president of National Permanent Savings and Loan.