The scenario is becoming all too familiar. An afternoon newspaper editor assembles a shaken staff, and announces that the paper's future is grim. It happened in July in Washington, and in August in Philadelphia and New York.

This week, the scene was played out here, at the 208-year-old Baltimore News American, but with a different twist. By late this afternoon, company officials had laid off 43 of the paper's 750 full-time employes, about half of them in the news department of 150 people. Reporters said they were told on Thursday that layoffs throughout the paper would exceed 100, but a company spokesman said today there would be no more cuts.

While reporters and a former editor variously called the cuts "shattering" and "demoralizing," there is no hint that the Hearst Corporation, owner of faltering dailies in Boston, Los Angeles and Seattle, plans to fold its struggling afternoon newspaper here. In fact, publisher B. Maurice Sparby said Hearst and the paper "intend to be here for a long, long time."

Sparby and business officials have portrayed the cuts as a belt-tightening campaign aimed largely at strengthening The News American, which until 1968 had the highest circulation in this three-newspaper town, but now runs third. They said they will not allow the paper to become as unprofitable as The Washington Star, which was losing $20 million a year when it was closed in August by Time Inc.

"This is very much in keeping with Hearst's philosophy that the paper has a better chance of gaining excellence if it's in a better financial position to operate," said one editor. "Of course, I don't expect reporters to agree with that."

Indeed, many reporters do not, saying in interviews today that they view the cuts as a pullback by Hearst from what has recently been a spirited, if little noticed, newspaper war with the venerable Sunpapers. Last week, 16 editors sent a letter to Hearst headquarters in New York citing recent improvements in the paper's editorial quality --including its ranking as a finalist in the 1980 Pulitzer Prize competition for local news --and saying that the gains would be undermined by layoffs.

"This has a shattering impact on the paper," said former editor Jon Katz, who was largely identified with the paper's recent rebound and who resigned last month to become managing editor of The Dallas Times Herald.

The News American's news staff of 150, weighted with young, aggressive recruits, was cut this week by 30, including 21 full-time employes. The features, art and photography staffs were reduced from 45 to 23, following layoffs and reassignments, according to reporters and editors. Travel budgets were cut deeply, and the sports writer who covers University of Maryland football will not be sent to cover this week's away-game with the University of Florida.

Editors were busy today shifting feature writers into slots left by the dismissed reporters, and company officials insisted that local news coverage would not suffer as a result of the layoffs.

Six senior writers and editors resigned voluntarily, and more than 10 others said they are looking for jobs because they expect the paper's quality and spirit to decline.

"It's a very deep, personal decision for me," said deputy sports editor Mike Marlow, 33, who came to the paper seven years ago as a high school sports reporter and resigned Thursday. "I've lived in Baltimore all my life. I love the place and I don't want to move. But for the last three years, we've upgraded this into a fine sports section, and with all that's happening, it's going to regress to such an extent that I wouldn't feel comfortable working for it."

Sparby did not return a reporter's telephone calls or requests for interviews, and Hearst officials in New York declined to comment on the changes. Company officials would not confirm how many reductions had been made in each department, but employes said six of 33 pressmen were laid off, and two in the promotion department. Other figures were not yet available.

The Hearst Corporation's changes in the paper, which it has owned for almost 60 years, began about three years ago, with the hiring of respected editors and experienced business managers.

Considered at the time one of the worst big-city dailies in the country, the paper improved dramatically as dozens of young writers joined the staff and began producing lively features and investigative reports. There was an attempt to link the paper's new image with the much-publicized efforts of the city itself to achieve a renaissance, and Katz said he was promised there would be no cuts in the news staff while he was there.

But while there were also improvements throughout the business staff, there was little coordination between the news department changes and the efforts in promotion, circulation and advertising, officials said. That, combined with the dismal economics of afternoon papers, particularly in the Northeast, prevented the paper from reversing a familiar downward spiral in the paper's share of Baltimore advertising and readership.

The same pattern was exhibited at The Washington Star and at The Bulletin in Philadelphia, which threatened to fold in August until unions agreed to accept wage cuts. At the same time, The New York Daily News announced the folding of its afternoon edition, Daily News Tonight.

In Baltimore, News American officials say they still have hope because the city has a large, blue-collar population, which has traditionally supported afternoon papers. The combined circulation of the two evening papers is 312,000, compared to the morning Sun's 178,960.

Business executives said today they are redoubling their efforts to recruit advertisers and readers and have advanced deadlines to get the paper on the street earlier. But 24-year-old Tim Kurkjian, a sports writer who was laid off this week, isn't betting on their success.

Kurkjian is now a double victim of the afternoon newspaper crisis, having come to The News American from The Washington Star, where he worked for three years until losing his job when the paper closed. "They called me on the phone yesterday and said, 'Bad news, you've been laid off,' " Kurkjian said. "I said, geez, it seems someone called me with that news two months ago . . . I've had two papers go out from under me. Maybe I'll try to find a morning paper somewhere."