Three hours at the opera house might not sound like your idea of a Sunday afternoon. But what if you could spread out a blanket on the Mall, pop open a picnic basket and watch the show at no cost?

To celebrate its 50th-anniversary season, Washington National Opera will present a free simulcast of its new production of George Gershwin's "Porgy and Bess" on the Mall on Nov. 6, the company announced yesterday. The 2 p.m. performance will be transmitted live from the Kennedy Center Opera House and shown on a gigantic video screen, 18 by 32 feet, that will be located near the Capitol, with speakers set up for sound.

Although large screens have been used to let audiences view close-ups of musicians while they were playing on the Mall, this is believed to be the first time that a performance originating elsewhere will have been transmitted there live. The production costs -- estimated at $300,000 on top of the usual expenses of putting on an opera at the Kennedy Center -- will be met by private donations from board members. According to Suzanne Stephens, a spokeswoman for the WNO, the event will not cost taxpayers a penny. Working through the National Park Service, WNO will pay all costs for security, first aid, trash removal, information stations, rangers on the site, sanitation and other necessities.

"Porgy and Bess," created for and (by decree of the Gershwin estate) always sung by an all-black cast, is a slice-of-life drama set in a poor African American neighborhood in Charleston, S.C. The 1935 opera, far and away Gershwin's most ambitious work, contains some of his most famous songs, including "Summertime," "Bess, You Is My Woman Now," and "It Ain't Necessarily So."

The WNO production, which opens Oct. 29 at the Kennedy Center, will feature Gordon Hawkins and Indira Mahajan in the title roles, and will be directed by Francesca Zambello. Wayne Marshall will conduct the Washington National Opera Orchestra and Chorus. There will be 10 performances through Nov. 19. A ticket to attend the Nov. 6 performance at the center's Opera House costs $102 to $190.

WNO has never before staged "Porgy and Bess," which is far better known for its arias and duets -- some of which have been sung and recorded by hundreds of artists -- than in its entirety. Indeed, much of the music will be unfamiliar to all but the most ardent operaphile.

"For the past 15 years, I have been doing simulcasts in cities such as Munich, Vienna and London," WNO General Director Placido Domingo said yesterday. "They are always so exciting -- people come and pay great attention, people who cannot always come to the theater but want to see and hear a great opera, people who love music. This is a great American opera, made for the Washington National Opera, made for Washington, made for the Mall."

According to John Pohanka, board chairman of WNO, the decision to present "Porgy" on the Mall arose during discussions of the best way to commemorate the troupe's anniversary.

"I want more people to know about opera," he said yesterday. "If you like theater, you should like opera, for good opera is good theater. 'Porgy' is an opera that everybody should be able to relate to, with famous melodies and a good story.

"There is a large African American population in Washington and, because there is such poor music education in our schools these days -- not just here but all over the country -- probably a lot of people who would love this opera don't yet know that it exists."

Michael R. Sonnenreich, WNO's president, said "Porgy and Bess" is an "ideal work to expand our audience. One thing we've been trying to do is get younger people interested in opera -- high school students, university students, young professionals. They'll be able to walk away when 'Porgy' is over humming the tunes, just as they might when leaving a Broadway show. And if this sort of event is successful, as it has been in Europe, we'll certainly consider doing it again."

Washington already has its own connection to Gershwin's opera. Todd Duncan (1903-1998), the elegant, honey-smooth baritone who created the role of Porgy, lived and taught singing here for almost 70 years, a mentor for generations of young musicians.

Duncan sang Porgy not only throughout the original Broadway production of 124 performances in 1935 but in revivals in 1937 and 1942. In 1953, there was a celebrated production of "Porgy and Bess" at the National Theatre, with William Warfield, Leontyne Price and Cab Calloway.

Pohanka declined to identify the trustees who paid the additional costs for the Mall event. "There were a number of people involved, and a range of gifts. It wasn't just one person or even a small group. This is a gift to the city from all the trustees."

Pohanka expressed some anxiety about Washington's unpredictable November weather. "That's a gamble, no doubt about it," he said. "We're hoping for a nice day. Still, people bundle up and go to Redskins games when it's snowing, so we hope some of that same crowd will come out for 'Porgy and Bess.' "

Indira Mahajan, left, will sing Bess to Gordon Hawkins's Porgy when the WNO's "Porgy and Bess" is simulcast on the Mall on Nov. 6.