HOUSTON, Texas (CNN) -- A weakened but still powerful Hurricane Rita continued its march Friday toward the Texas-Louisiana coast, with forecasters saying the storm could possibly strengthen before making landfall early Saturday.Ahead of the hurricane, highways were overloaded with frustrated evacuees.Max Mayfield, director of the National Hurricane Center in Miami, Florida, said Rita will hit a deep trench of warm water and could intensify before landfall, possibly to Category 5 status. The storm had attained Category 5 status before losing some of its strength Thursday and falling to Category 4. Mayfield said forecasters expect Rita to come ashore Saturday morning, likely between Galveston, Texas, and the Louisiana border."This is still a very, very dangerous Category 4 hurricane. We'll likely see some fluctuations. ... but the wise thing to do is to go ahead and plan for a Category 4 hurricane making landfall," Mayfield said.