With no technical problems at pad 39A, the shuttle Endeavour's countdown continues to tick smoothly toward launch Thursday on a space station crew rotation mission. But forecasters say the weather outlook hasn't changed and there's still a 60 percent chance of thunderstorms that could force a delay.

If you're a person who believes the glass is half full rather than half empty, Endeavour's crew has a reasonable shot at getting off the ground Thursday. But the glass definitely starts getting empty on Friday and Saturday, with the outlook 70 percent "no go" both days. Weather officers say they don't expect much of a break until early next week.

But readers should take launch percentages with a grain of salt. As former launch director and weatherman Bob Sieck used to say, it doesn't matter what the forecasters predict, it's 50-50 on launch day.

Otherwise, work at pad 39A continues per the countdown. Last night, engineers completed loading liquid hydrogen and oxygen into the shuttle to power its electricity producing fuel cells. The team is currently working through a series of main engine tests and readying pad systems for launch.

"We're right on schedule and we're tracking no technical issues," said NASA test director Pete Nickolenko. "All of our flight and ground systems are in great shape, the launch team is focused and ready to go and we're all looking forward to launch on Thursday."

Endeavour's actual five-minute launch window will open sometime during a four-hour launch period that begins at 4 p.m. Thursday. The exact launch time, which has been withheld under a post Sept. 11 security policy, will be released later today.