(CNN) The vicious weather that wrecked parts of Missouri and the Midwest is headed east , but for Arkansas, which has already faced tornadoes and deadly flooding this week, it appears the disaster is only beginning to unfold.

The Arkansas River, the country's sixth longest, already pushed past its banks upstream, deluging parts of Oklahoma. Now it's predicted to bring crest records to the state that shares its name -- not just Thursday, but through next week.

Exacerbating fears among residents and officials is the state's levee system, portions of which, they say, may not be high enough or strong enough to withstand the water.

"Levees remain a concern as they have never held back as much water for as much time as they have in the past," the Arkansas Department of Emergency Management said Wednesday.

Watching the levees

The Army Corps of Engineers and the Arkansas Forestry Commission are patrolling the levees, some of which are already leaking, the department said. The Civil Air Patrol is also photographing the levees so officials can take proactive measures where possible.

Brad Hindley and his son, Bart, pull a boat Wednesday to Brad's home in Fort Smith, Arkansas.

The Corps and Arkansas National Guard have also moved sandbag-filling machines to affected areas. Voluntary evacuations are underway.

"We are watching for a couple of levees that could breach, and if that breach threat becomes imminent then we could issue mandatory evacuations," Department of Emergency Management spokeswoman Melody Daniel told CNN.

Preliminary analysis indicates that flooding could affect thousands of homes in 14 counties along the river. Some could experience only minor damage, Daniel said, but others could be destroyed.

In Fort Smith, on the Oklahoma line, the Arkansas River wraps around the northern half of the city. Resident John Glidewell told CNN on Thursday that floodwaters are already up to his thigh.

"Looters will be shot!!" reads a sign in front of a home on Turtle Bay in Fort Smith.

In anticipation of the flooding, he and his wife began moving their belongings to a relative's home they inherited two years ago. It sits a few streets away. He's thankful to have a place to live, he said.

"God was watching over us," he said.

Arkansas River to break records

Forecasters said the river will crest Thursday afternoon in Van Buren, on the other side of the river from Fort Smith, at a record 40.5 feet.

To the east, in Barling, police Officer James Breeden told CNN, "This is the highest the river has ever been in recorded history."

Floodwaters surround a home Wednesday in Fort Smith.

As the water moves southeast through the state, more crest records are expected, pushing the Arkansas well over flood stage, according to the National Weather Service:

• in Ozark on Friday (375.5 feet)

• in Dardanelle and Morrilton on Saturday (45.5 and 43 feet, respectively)

• in Toad Suck on Sunday (285.5 feet)

• in Pendleton on June 7 (36 feet).

While not setting records, the river is expected to crest Tuesday in Little Rock at 28 feet, which is 5 feet above flood stage, and two days later in Pine Bluff, where the waterway is predicted to reach 49 feet, which is 7 feet above flood stage, the weather service said.

Aerial images show that, days before the river is predicted to crest, it is already flooding locales in Logan County and Little Rock. Logan County Sheriff Jason Massey announced numerous road closures.

Two levees -- one of them in Logan County along state Highway 309 -- have overtopped so far, but none has failed, Daniel said.

Water overtops a levee in Logan County, Arkansas, near state Highway 309, drone footage shows.

"This is looking to be record breaking all along the Arkansas River, and this is something we have never seen before," she said.

Downstream in Dardanelle, a 110-bed nursing home has pre-emptively moved residents to safer ground, Mayor Jimmy Witt said early Wednesday.

'It surpasses all Arkansas flooding'

Gov. Asa Hutchinson took an aerial tour of the flooded area Thursday, flying out of Fort Smith. US Sens. John Boozman and Tom Cotton and US Rep. Bruce Westerman joined him on the plane, which flew over some of the hundreds of homes and thousands of acres of farmland damaged by the floodwaters, Hutchinson said.

"It's hard to imagine the magnitude of the flooding. It's difficult to comprehend," the governor said afterward. "We've never seen this before. We've never had to deal with this before, so there are a lot of unknowns."

Hutchinson previously announced additional funds for disaster relief Wednesday and requested in a letter that President Donald Trump declare emergencies for 15 Arkansas counties, a number he expects to increase. He also briefed Trump over the phone, he said, and the President told him the Federal Emergency Management Agency was "on board."

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"He assured us of the federal assistance that will be available," the governor said, adding that Trump called him as soon as he returned from his trip to Japan.

Flooding has already taken one life in Arkansas, police said. A 64-year-old man appears to have driven his Suzuki SUV around a barricade into a flooded roadway Tuesday. He later drowned, said Breeden, the Barling police officer. The man's body was recovered near Fort Chaffee, southeast of Fort Smith.