Weather officials said Wednesday that an advancing storm has reduced the odds to one in five that Atlantis and its five astronauts can be launched Thursday on a secret military satellite mission.

A leaking tire on the shuttle's main landing gear was a less bothersome concern.NASA's 21-member Mission Management Team met to assess the worsening forecast, which called for winds up to 24 mph, heavy clouds and the possibility of light rain at the planned launch time.

Because all details of the flight are classified, NASA has said only that the planned launch time was between 6:32 a.m. and 9:32 a.m. Sources said liftoff was set for about 7 a.m.

Capt. Ken Warren, an Air Force spokesman, said the biggest problem was a prediction of a heavy cloud layer over the runway here where Atlantis would land if there were an emergency shortly after liftoff.

"It is not looking very good for a return-to-launch-site abort," Warren said.

Mission rules call for a cloud ceiling above 8,000 feet over the runway. The forecast is for 4,000 feet. Strong crosswinds also could be a deterrent, Warren said.

Warren said the weather odds for a launch itself were 60 percent. But they dropped to 20 percent with the emergency landing requirements factored in.

The problem was a cold front carrying thunderstorms stretching from the Great Lakes to the Gulf Coast which Warren said should reach the Cape Canaveral area early Thursday.

If the forecast apeared hopeless, launch managers most likely would delay the liftoff before technicians start pumping more than half a million gallons of liquid hydrogen and liquid oxygen into Atlantis' external fuel tank. That was scheduled to start late tonight.

At the launch pad, NASA reported the countdown was on schedule. Early Wednesday the clock was stopped for a planned 16 hour, 20 minute hold at the 11-hour mark.