The Senate Commerce Committee signaled the way for dramatic changes in the Federal Communications Commission yesterday by warmly encouraging Chairman-designee Mark Fowler to make substantial changes in commission management.

Like their counterparts on the House telecommunications subcommittee Thursday, the committee also moved closer to enacting the first authorization legislation for the FCC, a move that will give the two congressional committees a tighter grip on FCC activities.

The committee is expected to confirm by poll the Fowler nomination for an FCC term until 1986. Fowler, 39 is a Washington private-broadcasting lawyer, former attorney for the Reagan campaign and Reagan administration transition official. He could take office as soon as the end of next week.

In comments before the committee yesterday, Fowler emphasized that he would stress industry deregulation, cooperation with Congress and improved FCC management during a time when the agency is faced with major technological changes in the communications industry and equally significant revisions in the laws the agency administers.

He chided the FCC under his predecessor, Charles Ferris, on several fronts, calling the agency's efforts to lease office space to move its headquarters to Roslyn "not proper." Fowler was critical of the agency's efforts to encourage new AM radio stations by reducing the separations between frequencies, warning of interference problems, and said the FCC had moved too quickly in accepting applications for new low-power television stations.

Fowler said he is "very sympathic with the goals" of the FCC's landmark Computer II decision, which deregulated facets of the telephone business and permits American Telephone & Telegraph Co. to enter unregulated fields though a separate subsidiary. He also issued tentative support for Republican-sponsored legislation that would put into law many of the principles in that controversial FCC decision.

As Fowler's nomination appears ready to sail through the Senate, similar suport is likely for FCC nominee Mimi Weyforth, an aide to Sen. Robert Packwood (R-Ore.), adn Henry Rivera, an Albuquerque lawyer who Reagan is expected to nominate soon to another FCC seat. Current Commissioner James Quello is expected gain renomination.

Meanwhile, Sen. Barry Goldwater (R-Ariz.), the chairman of the communications subcommittee, was critical of FCC management in remarks opening a later hearing on the FCC authorization bill. As the House panel was sharply critical of the FCC Thursday, Goldwater said a "fundamental commission shortfall is its failure to establish goals and objectives."

Goldwater was generally supported by representatives of the General Accounting Office, who for the last five years consistently have criticized the operations, if not the policy thrust, of the FCC.