Discovery?s seven astronauts planned to spend the last day testing the shuttle?s flight control system, stowing items, deploying a tiny satellite and giving their last media interviews from space.
NASA managers in Houston, meanwhile, faced a series of complicated trade-offs about where to land the spacecraft.
The forecast calls for low clouds and showers at Kennedy Space Center, where Discovery is slated to land Friday.
Crosswinds are expected at the primary backup landing site at Edwards Air Force Base in California. The weather looks good at another backup site in New Mexico, but it is rarely used and lacks equipment, meaning a landing there would give NASA logistical headaches.