"All neighborhoods, and possibly entire coastal communities, will be inundated during the period of peak storm tide," forecasters said in an unusually strong warning. "Persons not heeding evacuation orders in single-family one- or two-story homes will face certain death."

Residents of larger buildings risk being cut off by flooded or washed-out roads, the warning said.

The hurricane's center was expected to come ashore late Friday. But the National Hurricane Center in Miami said the large storm, with hurricane-force winds extending 115 miles from the center and tropical storm winds 265 miles, will make itself felt hours earlier.

At 11 p.m. EDT, the center was 445 miles east-southeast of Corpus Christi and 340 miles southeast of Galveston, moving west-northwest at 12 mph.

A hurricane warning was posted from Morgan City, La., on the coast due south of Baton Rouge, to the Corpus Christi area in Texas. A tropical storm warning was posted for eastern Louisiana, including New Orleans, Mississippi and the rest of the Texas coast.

While Ike remained a Category 2 hurricane with maximum winds of about 100 mph, forecasters said it would gain strength Friday.

Houston Thursday began a mandatory evacuation of residents in low-lying areas.