Washington Post Co. Chairman Katharine Graham said yesterday that communications firm currently is ahead of last year's record levels.

But the outlook for the last six months of 1979 is "unclear," Graham told stockholders at the company's annual meeting here. If economists' forecasts of recession turn out to be accurate, "we would obviously be affected," she stated.

Specifically, Graham noted that advance bookings for second-half advertisements in the Post Co.'s Newsweek magazine are down, with advertisers apparently hesistant to cimmit ad funds far in advance. In the event of a sour economy or an automobile workers' strike later in the year, earnings of the newsweek division "could decline," Graham said in an address to the meeting.

To date, Newsweek ad pages are up some 5 percent from the 1978 pace.

In the company's broadcasting division, which operates television stations in Detroit, Miami, Jacksnville and Hartford, second-quarter advertising orders are "nicely ahead of last year" and 1979 is expected to result in "excellent" performance, Graham added.

Among newpaper operations, advertising and circulation gains are continuing at The Washington Post and Everett, Wash., Herald, which recently started circulation paper to increase penetration of its market north of Seatttle.

But circulation is down at the firm's Trenton, N.J. Times, which Graham conceded is "an obvious concern." Starting June 4, the New Jersey afternoon daily will add a morning street-sales edition, she reported.

At the company's flagship newspaper, The Post, Graham noted that in 1979 a number of changes had been made to expand and improve the editorial product offered to readers. She cited a new weather map package, Sunday food section, daily "Style Plus" pages and the opening of a foreign reporting bureau in West Africa. Looking ahead, Graham repeated earlier Post Co. statements focusing on existing properties as the major source of business growth. At the same time, she emphasized that the communications company is interested in acquistions in this country or abroad-if and when the right opportunity shows up-and would be willing to assume "substantial debt" in such an expansion.

In the meantime , the Post Co. has "found one amazingly good opportunity"-buying its own shares in the marketplace since 1975. Directors of the firm yesterday approved plans to acquire an additional 500,000 shares of its class B stock, mainly block purchases, bringing to about 650,000 the number of shares now authorized for repurchase.

There are about 12.5 million class B shares currently outstanding. The firm has repurchased about 4.4 million shares in recent annual meetings of the Post Co., most of yesterday's two-hour session was devoted to questions or criticism of management decisions and Washington Post editorials and news reporting by Reed Irvine, of the Washington-based Accurracy in Media; and the Rev. Lester Kinsolving, a gadfly journalist. CAPTION: Picture, Washington Post Co. President Mark Meagher and Chairman Katharine Graham. By Douglas Chevalier - The Washington Post*