JEAN LAFITTE, La. » The center of Tropical Storm Lee lurched across Louisiana’s Gulf Coast early Sunday, dumping torrential rains that threatened flooding in low-lying communities in a foreshadowing of what cities further inland could face in coming days.

Lee’s center crawled ashore before dawn after the vast, soggy storm system spent hours during the weekend hovering in the northernmost Gulf of Mexico. The storm’s slow crawl to the north gave more time for its drenching rain bands to pelt a wide swath of vulnerable coastline, raising the flood threat.

By Sunday, at least 6 to 10 inches of rain had fallen in some spots along the Louisiana and Mississippi coasts, and the National Weather Service warned there was a threat of extensive flooding and flash floods because of the storm’s slow, meandering jog inland.

The drenching rainbands were expected to head northward into the Tennessee Valley later in the week as forecasters warned that 10 to 15 inches of rain were possible along the central Gulf Coast and up to 20 inches in isolated spots.

No injuries were reported so far from the storm. But even before Lee swept ashore, there were scattered instances of water entering low-lying homes and businesses in Louisiana’s bayou country — a region of fast-eroding wetlands long vulnerable to hurricanes and tropical storms. The storm prompted evacuations in bayou towns such as Jean Lafitte. Thousands were without power.

Late Saturday, lifelong Jean Lafitte resident Brad Zinet was riding out the storm in his mobile home mounted on pilings. He was hoping it wouldn’t take on water.

"We got nowhere to go. We’re just getting everything put up out of the way and hope for the best," said the 31-year-old plumber.

"This is a way of life around here," he added. "You just do the best you can and ride it out."

A week after Hurricane Irene caused massive flooding and claimed at least 46 lives as it barreled up the East Coast, President Barack Obama was heading to northern New Jersey later Sunday for a first-hand look at the damage while keeping an eye on Lee.

The president was to visit Paterson, N.J., where the Passaic River swept through the once-booming factory town of 150,000, flooded its downtown and forced hundreds to evacuate.

At 5 a.m. EDT, the National Hurricane Center in Miami said Lee’s center had come ashore on the Louisiana coast about 50 miles southwest of Lafayette. Maximum sustained winds were reported to be 45 mph as the storm headed to the north at 2 mph.

Tropical storm warnings stretched from near the Louisiana-Texas state line to Destin, Fla.

Forecasters said Lee was expected to gradually turn more to the northeast and, after nightfall, o the east-northeast. On that predicted track, forecasters said, Lee’s core would move slowly over southern Louisiana during the day and night.

Although Lee’s expected to weaken in coming days, the system was expected to unleash heavy rains over a wide area of the central Gulf Coast and then spread that precipitation into the Tennessee Valley, forecasters said.

To the east, coastal businesses were suffering. Alabama beaches that would normally be packed for the Labor Day holiday were largely empty, and rough seas closed the Port of Mobile. Mississippi’s coastal casinos, however, were open and reporting brisk business.

Officials in some suburban and rural areas of southeast Louisiana reported more than 10 inches had already fallen even before Lee reached the coast.

In New Orleans, sporadic downpours caused some street flooding Saturday, but pumps were sucking up the water and sending it into Lake Pontchartrain. Officials said the levees were doing their job in the city that is still recovering from the deadly Hurricane Katrina a half decade ago.

New Orleans Mayor Mitch Landrieu warned residents not to let their guard down, saying: "We’re not out of the woods. Don’t go to sleep on this storm."

To the east, coastal Mississippi officials were bracing for the storm to move further into the state. "We’ve been getting some pretty good onshore rains," said Jackson County emergency director Donald Langham.

Harrison County officials said travel on U.S. Highway 90 had become hazardous because winds from Lee have pushed sand from beach onto the eastbound lanes and the rain has created a situation where drivers cannot see the roadway.

"This layer of sand has gotten up on the highway and you can’t determine if you’re on the road, up on the median or the curb," said emergency director Rupert Lacy.

Flooding in Hancock County left several roadways impassable, and the rain on parts of Interstate 10 at times has been so heavy that visibility was down to only a few feet.

In Alabama, rough seas forced the closure of the Port of Mobile. Pockets of heavy rain pounded the beaches Saturday, and strong winds whipped up the surf and bowed palm trees. But just a couple miles inland, wind and rain dropped significantly.

Wet and windy conditions hovered over Dauphin Island, a barrier island in the Gulf, but conditions weren’t too threatening, Mayor Jeff Collier said. High surf caused some roads to flood, but all were still passable Saturday afternoon.

Precautions were taken to secure anything that could be swept away by wind or waves, and Labor Day concerts and other festivities were canceled.

"The weekend is literally a wash," Collier said. "It’s really a shame that it happened on a holiday weekend."

Beaches that would normally be packed were nearly empty. Melinda Fondren, who moved to Gulf Shores about three months ago, visited the beach to experience her first tropical storm.

"I’m excited but a little afraid of the storm surge," she said, adding that her middle name is Lee. "I’ve been telling my family that I hit Gulf Shores twice."

Elsewhere, the National Hurricane Center reported, Tropical Storm Katia was trekking across open ocean some 370 miles northeast of the Northern Leeward Islands but no coastal watches or warnings were in effect with the storm so far out to sea.

The center said Katia had top sustained winds of 70 mph and was moving at 12 mph with little change in recent hours. But forecasters said Katia could during the day regain the hurricane status it had earlier.