Texas is bracing for potentially catastrophic flooding and winds as Hurricane Harvey intensified Thursday and cruised toward a landfall near Corpus Christi late tonight or early Saturday. The National Hurricane Center described Harvey's sudden strengthening as "astounding." The storm is expected to strike as a Category 3 hurricane — meaning with winds greater than 111 miles per hour — making it the most powerful storm to make landfall in the United States since Hurricane Wilma hit South Florida in 2005. Despite the increasingly alarming forecasts, officials in Corpus Christi as of Thursday evening had held off on ordering mandatory evacuations of the city, which includes a great deal of low-lying land and a barrier island. "I'm not going to risk our police and fire people trying to drag somebody out of the house if they don't want to go," Mayor Joe McComb said at an afternoon news conference. As of 11 p.m., the storm has maximum sustained winds of 85 mph and was moving northwest at 10 mph. LIVE RADAR: Interactive storm track, hourly outlooks, 10-day forecasts and weather alerts The surprise hurricane is poised to be the first major test of disaster response for the Trump administration, whose appointee to lead the Federal Emergency Management Agency, William "Brock" Long, was confirmed in June. "With Harvey now strengthening at a faster rate than indicated in previous advisories, the intensity forecast has become quite concerning," the National Hurricane Center wrote in a Thursday morning advisory. "Harvey has intensified quickly this morning, and is now forecast to be a major hurricane at landfall, bringing life-threatening storm surge, rainfall, and wind hazards to portions of the Texas coast." DOWNLOAD: Get the tbo Weather App and see where storms are headed Harvey had disintegrated into a tropical depression as it crossed the Yucatan Peninsula into the western Gulf of Mexico this week. But it reorganized itself over the hot gulf waters, forming a new, 15-mile-wide eye and rapidly evolved into a hurricane by midday Thursday. It then drifted northwest at 10 mph and was forecast to slow down a bit, giving it time to siphon energy from the steamy Gulf of Mexico. When it comes ashore, forecasters said, it could have sustained winds of 125 mph, with a 12-foot storm surge. Worse, it is projected to stall on the Texas coast for several days, which could dump historic amounts of rain, with some places seeing as much as 35 inches, the hurricane center said. The storm is forecast to meander to the east, deluging Houston and possibly New Orleans next week. "Trying not to be dramatic, but I fear epic flood catastrophe," tweeted Marshall Shepherd, a past-president of the American Meteorological Society. "Somebody is going to get a rainstorm to tell their grandkids about," said Bill Read, a past director of the National Hurricane Center. HURRICANE GUIDE: Emergency information, tracking map and storm resources Officials in Corpus Christi scrambled Thursday to respond to the sudden hurricane threat but decided against mandatory evacuations. Instead, officials instructed residents on the barrier island and low-lying areas inland to evacuate on a voluntary basis. "We are up to and almost at the threshold of mandatory evacuations, but we are not going to cross that line right now," McComb said. "We are going in the strongest possible terms to encourage the residents in the low-lying areas, as they say, 'Get out of Dodge.' " Nueces County Judge Samuel Neal, who is overseeing the county's emergency response, did not rule out mandatory evacuations but said such a move would not be done lightly. "We will do it if we feel it's necessary," he said. "This would create a major, major impact on the way a lot of people do business." Texas Gov. Greg Abbott declared a pre-emptive state of disaster in 30 counties, including Harris County, home to Houston, the fourth most-populated city in the country. Charles Bujan, mayor of the barrier-island city of Port Aransas, Texas, ordered all citizens to evacuate except those working as emergency responders. Long, the new FEMA director, has stressed in interviews with the Washington Post that state and local officials need to improve their emergency readiness and recognize that it is not the federal government's responsibility alone to respond to natural disasters. Long has also urged citizens to understand that they will often be their own first responders in a crisis. "People need to be the help before the help arrives," he said earlier this month. Harvey would be the first hurricane to hit Texas since Ike, a high Category 2 storm, made landfall in September 2008 in Galveston and caused tens of billions of dollars in property damage.