Channel 5 announced yesterday that Pat Mitchell, a Boston television personality, will be the new host of its influential noontime talk show, "Panorama."

Like her predecessor, Maury Povich, Mitchell will also handle the noon news segment of the two-hour midday program. More than 250 applicants had sought the job since Povich resigned last month to accept an anchor spot an WMAQ in Chicago. For the past five years. Mitchell has been a field reporter and talk-show host for WBZ in Boston.

"Panorama" producer Phyllis MaGrady said yesterday she had first spotted Mitchell doing a live interview two years earlier while visiting that city.

"She's hard-hitting, blonde and very pretty," said McGrady. "We'd been thinking of hiring a man, but in a couple of tryouts here in the last couple of weeks Pat has been very, very impressive."

Mitchell has a graduate degree from the University of Georgia and has taught at both the University of Virginia and Harvard University. She was writing her first article for "Look" magazine when it folded in 1971.

Mitchell is due to debut on Monday. Jan. 31, three days after "Panorama" celebrates its 10th birthday.

Salary terms were not announced but sources indicate the range could be between $55,000 and $60,000. WTTG, which is owned by Metromedia, has plans to eventually syndicate the noontime show.

Povich had been with the program since its inception in January 1966, first as co-host and then as host. He will receive $100,000 a year as anchorman for WmAQ-TV in Chicago, an NBC-owned station.

When news of his resignation surfaced. McGrady and other WTTG executivies were swamped by jobseekers after the high-visibility host spot.

"Panorama" does not enjoy big noontime ratings compared to net work soap operas and game shows, but its audience includes some of the biggest names in the capital.

Several news stories have been generated by on-the-air phone calls from powerful viewers miffed by a guest's comment.

Among those who actively sought the job were White House press secretary Ron Nessen; his predecessor Jerry TerHorst; former New York mayor John Lindsay; one-time Robert Kennedy aide Frank Mankiewicz; New York radio personality Barry Farber, and local man-about-town Steve Martindale.

What amazed McGrady, however, was how many doctors, chiropractors, dentists and lawyers, none of whom had ever appeared on television, felt themselves capable of stepping into the $50,000-a-year spot.

"It got so I didn't dare go to parties there for a while," McGrady recalled yesterday.

She said most of the applicants were TV performers in markets as far away as Omaha. Nashville and Detroit, all seeking exposure in mediaconscious Washington, the eight largest TV market in the country.