Live: Weather forecast moves to "perfect"

The weather forecast has just been upgraded to a 100 percent chance of acceptable launch conditions.

The sky is free of the clouds we saw gathering around the launch complex. Clouds were the main concern in the launch forecast issued this morning, which gave NASA an 80 percent of acceptable conditions at the 7:43 p.m. liftoff time.

Within the last hour, the weather forecast was changed as conditions improved.

The shuttle weather officer, Kathy Winters, is confident that conditions will remain stable until liftoff.