Overcast skies forecast for Cape Canaveral tonight could delay NASA's planned launch of the space shuttle Discovery. The launch chance was downgraded to 40% because of the weather.
"The forecast has trended for the worse right now," said Kathy Winters, shuttle weather officer.
NASA won't launch with low clouds because officials want to track it visually and allow visibility in case the astronauts need to make an emergency landing. NASA has four launch opportunities over five days, if need be, to start the mission.
Discovery's seven astronauts plan to rewire the International Space Station, deliver a two-ton addition and replace one of the station's three crew members.