(CNN) -- A weakened Isaac moved over Arkansas on Friday, leaving weary residents in Southern states digging out of its muddy mess and hundreds of thousands without power.
The weakened storm, now a tropical depression, is expected to move over southern Missouri later in the day after slamming the Gulf Coast as a powerful Category 1 hurricane Tuesday.
On Friday, the storm was about 25 miles northeast of Fort Smith, Arkansas, and flood and flash flood warnings were in effect in Arkansas, Mississippi and Louisiana. Isaac will bring heavy rainfall as it heads northeast into the Ohio River Valley on Saturday.
Isaac packed a punch as it crawled inland. At three people were dead and more than 827,000 customers were without electricity across Arkansas, Alabama, Louisiana and Mississippi as of late Thursday, utility companies said.
Republican presidential nominee Mitt Romney is visiting Louisiana to view storm damage, and President Barack Obama is canceling a Monday trip to Cleveland to visit the state.
Obama will be meeting with officials dealing with Isaac's impact and "making sure that unmet needs are being met and that the federal response led by FEMA (the Federal Emergency Management Agency) is helping citizens in the affected areas and the state and local officials who are responding to the storm," White House press secretary Jay Carney said.
Isaac made landfall on the anniversary of Hurricane Katrina, which devastated Louisiana seven years ago. That hurricane churned through the Gulf of Mexico and overwhelmed levees, resulting in 1,800 deaths.
"This is unbelievable. Deja vu, man," Billy Nungesser, the president of Plaquemines Parish, Louisiana, said Thursday as he surveyed Ironton town, which was inundated by floodwaters and sludge. "There is more water here than Katrina."
New Orleans Mayor Mitch Landrieu underscored that point.
"A hurricane that is a Category 1 that stays around for a long time can stress the system just like a Category 5, 4 or 3 that stays around for a short time. Secondly, just because it was Category 1 for some people, that doesn't mean it was a Category 1 for everybody. There are some individuals in the metropolitan area of New Orleans that have suffered damages in excess of what they suffered during Katrina."
In Plaquemines Parish, officials intentionally breached a levee to help drain floodwaters in nearby communities.
The bodies of a man and woman were found in 7 feet of water in the kitchen of a home in the parish, officials said late Thursday. An autopsy will determine the cause of the death of the couple, described as being in their 40s, Nungesser said.
In Tangipahoa, Parish President Gordon Burgess called for a mandatory evacuation for those living within a half-mile of the Tangipahoa River. Louisiana Gov. Bobby Jindal said the move was a precaution because if the dam were to break, it would only take 90 minutes for floodwaters to get to Kentwood, a town of about 2,200 residents.
Twenty-eight Louisiana parishes were under a boil-water advisory, health officials said.
In Mississippi, the storm had a "major impact," Gov. Phil Bryant said. A tow truck driver attempting to clear debris on a road was struck and killed by a falling tree, officials said.
An earthen dam on Lake Tangipahoa in Mississippi was holding its own and not leaking late Thursday, despite significant damage, according to the Pike County Emergency Management Agency.
Agency director Richard Coghlan said a "controlled breach" or spillway will be created at Percy Quin State Park's lake to relieve pressure and drain it.
Step by step, the Gulf Coast was working to get back to normal.
On Friday, the Coast Guard captain at the New Orleans port reopened the Mississippi River, from Baton Rouge to the mouth of the river, to limited vessel traffic.
"Although the Mississippi River was heavily impacted by the storm, the navigational channel is in good condition. The Coast Guard is working with the maritime industry to respond to a number of ship groundings and barge strandings along the riverbank caused by the river surge and high winds of the storm," the Coast Guard said.
Louis Armstrong New Orleans International Airport said Friday that flights have resumed and commercial power has been restored.
As Isaac moved into southern Arkansas, it brought the possibility of flash flooding and tornadoes.
"It's looking more disorganized, but it is still putting out quite a bit of rain," said Charles Dalton, a National Weather Service meteorologist in Little Rock.
Rainfall around Little Rock could total 5 inches by Friday, he said. Higher amounts were expected in southeastern Arkansas. Emergency crews are also trying to restore power to many.
CNN's Brian Todd and Joe Sterling contributed to this report.