The remnants of Tropical Storm Harvey gained strength in the Gulf of Mexico on Wednesday, prompting tropical storm and hurricane watches for heavy rains, strong winds and flooding that could threaten the Gulf Coast over the next 48 hours, forecasters said.

The National Hurricane Center had said the storm could make landfall, affecting the cities of Corpus Christi, Tex., Houston and New Orleans, among others.

The center updated its advisories on Wednesday, saying hurricane conditions were possible by Friday for coastal areas from Port Mansfield, Tex., northeast to San Luis Pass, which is 25 miles southwest of Galveston, Tex.