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Shuttle outlook gets slightly cloudier

Roberto Gonzalez / Getty Images

Photographers and observers place their cameras at the base of the space shuttle Endeavour's launch pad at Kennedy Space Center in Florida in preparation for Friday's scheduled liftoff.

The wild weather that is sweeping through America's Southeast has had a mild impact on the outlook for the shuttle Endeavour's final flight, with forecasters raising the chances of a delay in Friday's launch from 20 to 30 percent.

Right now, the weather is the only question mark about a flight that's expected to attract upwards of 700,000 spectators, including notables ranging from President Barack Obama and wounded U.S. Rep. Gabrielle Giffords to "Star Trek" actor LeVar Burton and gamer/astronaut Richard Garriott.

The skies over Kennedy Space Center in Florida were mostly sunny this morning, but chief weather officer Kathy Winters said that the tail end of a storm system that left a trail of destruction through Alabama was headed for the Florida coast.

"The weather is expected to get a little bit bad this evening," Winters told reporters.

If low clouds are still hanging around when it's time to launch, at 3:47 p.m. ET Friday, the launch would have to be delayed at least 24 hours. The potential cloud ceiling, added to the chance of unacceptably high crosswinds, led Winters and her fellow forecasters to downgrade the weather outlook from 80 percent positive to 70 percent positive. Which is still pretty positive, as weather forecasts go.

NASA test director Jeff Spaulding said the countdown was proceeding without any technical hitches. But if the launch has to be put on hold on Friday, whether for weather or for other reasons, Spaulding said NASA would still have at least three more opportunities for liftoff over the next week.

Notable launch
This launch is notable for several reasons: It marks Endeavour's final space outing before it heads for retirement at the California Science Center in Los Angeles. It'll be the second-to-last shuttle launch ever, setting the stage for Atlantis to close out the 30-year shuttle program this summer. Endeavour will be bringing up the $2 billion Alpha Magnetic Spectrometer, one of the biggest physics experiments ever launched into orbit. And perhaps most poignantly, the launch is the focus of a love story involving Giffords and her husband, Endeavour commander Mark Kelly.

Giffords, an Arizona Democrat who is recovering from a grave head wound sustained in January during a shooting attack in Tucson, was flown to Florida from her rehabilitation center in Houston to see the launch and take part in family festivities.

President Obama, along with his wife and two daughters, are due to witness the launch from the space center as well, in between a visit to storm-stricken Alabama and a commencement address at Miami Dade College. The last sitting president to attend a shuttle launch was Bill Clinton, who came to the Cape to see off senator-astronaut John Glenn in 1998. It's not yet clear whether the Obamas will be with Giffords or at a different secure location for the launch.

"We will be ready to accommodate, wherever that location is," Spaulding said. 

Tweeters in attendance
Other celebrities in attendance this time around include LeVar Burton, who played Geordi LaForge on "Star Trek: Next Generation"; and Seth Green, who has appeared in the "Austin Power" movies and a host of other films and TV shows. The actors are among 150 Twitter users who were invited to the launch to participate in a NASA tweetup, and they traded tweets for their own meetup at the Cape.

"Where are you, man?" Burton tweeted to the red-haired Green. "My Ginger detector is on the fritz?"

"Less than 20 feet away from you!" Green replied. "Why won't you say hi to me?!?"

Richard Garriott, the millionaire video-game developer who became the first son of a NASA astronaut to go into space himself in 2008, also tweeted that he was heading down to Florida to see the launch.

Spaulding told reporters that he and the rest of the launch team weren't changing their routine just because a high-profile audience was hoping to see Endeavour rise on Friday. "We do the exact same level of effort" in advance of every liftoff, he said, and there'd be no pressure to put on a show.

"Our team is really focused in on what we're doing here," he said.

More about the shuttle's final days:

Stay tuned for further updates from Kennedy Space Center, in Cosmic Log as well as in msnbc.com's space news section. You can join the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.