This story was updated at 2:32 p.m. EDT.
CAPE CANAVERAL, Fla. -- NASA's shuttle Atlantis and its astronaut crew will have to wait at least one more day before returning to Earth after poor weather thwarted a planned Thursday landing.
Nearby thunderstorms and a low cloud ceiling over NASA's Shuttle Landing Facility here at the Kennedy Space Center (KSC) prevented the Atlantis astronauts from completing their 13-day mission, but the weather woes were expected.
"If the weather does not cooperate, we will keep the vehicle safe and the crew safe and we'll just go around another day," NASA's entry flight director Norm Knight said.
Atlantis is now set to land Friday, with the first KSC opportunity at 2:18 p.m. EDT (1818 GMT).
The shuttle was slated to land here at KSC during one of two opportunities beginning at 1:55 p.m. EDT (1755 GMT). After weather conditions proved unacceptable for the first window, flight controllers kept the shuttle crew on standby for a possible 3:30 p.m. EDT (1939 GMT) landing.
"We looked as long and hard as we think is reasonable today," NASA astronaut Tony Antonelli, serving as spacecraft communicator in Mission Control, told Atlantis' STS-117 crew. "The rain showers and ceiling are going to keep us making it into Florida today."
Weather forecasts continue to predict low cloud cover and thunderstorms within 30 nautical miles (about 34 miles or 54 kilometers) of Atlantis' landing site. NASA shuttles do not land in rain because it can damage the orbiter's vital heat resistant tiles and require repairs.
Commanded by veteran shuttle astronaut Rick Sturckow, Atlantis' seven-astronaut crew successfully delivered new solar arrays and massive $367.3 million trusses to the International Space Station (ISS). The astronauts staged four spacewalks to install the new station components and deploy the arrays, pack away an older solar wing atop the ISS and swap out one member of the station's Expedition 15 crew.
The Atlantis crew also helped the ISS astronauts recover vital Russian computer systems that crashed last week and repaired a torn bit of thermal blanket on the shuttle's left aft engine pod.
Returning to Earth with Sturckow are Atlantis pilot Lee Archambault and mission specialists Patrick Forrester, Steven Swanson, James Reilly II, Danny Olivas and Sunita Williams, who is setting a world record for the longest duration spaceflight by a female astronaut.
Now in her 193rd day in space, Williams is ending just over six months in space after serving as a member of the space station's Expedition 14 and 15 crews. NASA astronaut Clayton Anderson, who launched spaceward with the STS-117 crew on June 8, replaced Williams to join Expedition 15 commander Fyodor Yurchikhin and Oleg Kotov aboard the station.
Atlantis has enough supplies to remain in orbit through Sunday, though mission managers want to land the shuttle by Saturday, weather permitting, and keep the final day in reserve in case the orbiter experiences a technical glitch.
On Friday, the orbiter could make a second attempt to land here at KSC at 3:54 p.m. EDT (1951 GMT).
At least two other landing opportunities, one at 5:24 p.m. (2124 GMT) and the other at 6:59 p.m. EDT (2259 GMT) are also available Friday at NASA's backup site on Edwards Air Force Base in California, though high headwinds are expected.
A third landing window at Edwards will also be available at 3:49 p.m. EDT (1949 GMT) will be available after a planned engine burn by the Atlantis crew later today, NASA said. That maneuver would allow Atlantis a chance of avoiding the expected high winds at Edwards should a landing at the backup site be required, the space agency said.
On Saturday and Sunday, a third option - Northrup Strip at White Sands Space Harbor in New Mexico - will also be available, though it is a third choice and not expected to be required.
Atlantis' STS-117 mission is NASA's first of up to four planned shuttle flights to continue assembly of the ISS in 2007.
NASA is broadcasting the space shuttle Atlantis' STS-117 mission live on NASA TV. Click here for mission updates and SPACE.com's video feed.