North Dakota Racing Against the Rising River

Cracks forming in an earthen levee holding back the swelling Red River reportedly have prompted officials to order the evacuation of a Fargo, N.D., neighborhood and a nursing home.

Mayor Dennis Walaker said residents were not in immediate danger and water was not flowing over the levee, the Associated Press reported, but officers were going door-to-door in the River Vili neighborood to order out residents of about 40 houses and the Riverview Estates nursing home.

The new threat emerged as the river headed toward an unprecedented crest that was sending Fargo-area residents into "uncharted territory," Walaker said today.

Officials predicted the Red River could crest as high as 43 feet this weekend -- two feet higher than forecasters had previously said.

VIDEO: Waterlogged Fargo Braces for CrestPlay

"No one has ever seen the river at this level in the city of Fargo since the beginning of history," Walaker said. "We need all the help we can get."

Volunteers scrambled to try to add one more foot of sandbags around the river while the city put final touches on an evacuation plan. The rising river waters forced city officials to call on thousands of additional volunteers Thursday in a race to raise the levees to 43 feet.

"To raise a whole foot is a monumental event," requiring millions of sandbags, a volunteer told ABC News.

The Red River, which divides North Dakota and Minnesota, stood at 39 feet this afternoon. The National Weather Service, which had predicted a crest of 41 feet by Saturday, said the waters could now reach 43 feet.

VIDEO: Twister Ravages Magee, Miss.Play

"I hope we're not doing this all for nothing," said Donna Decker, who was packing sandbags in Fargo's indoor stadium. "I just hope it works."

Scattered evacuations were reported south of the city, where Coast Guard air boats plucked residents George and Dorothy Sealy from their flooded home.

"I said, 'I'm not leaving.' I don't care, but overnight the basement took on water," Dorothy Sealy said from a stretcher.

Nursing homes in the city began to evacuate patients in an attempt to bring the most vulnerable to higher ground. North Dakota's largest city released evacuation plans late Thursday for its 92,000 residents.

VIDEO: Floods in North DakotaPlay

"If you know you need to get out, we need you to get out today," Cass County Sheriff Paul Laney told residents, warming of the conditions expected to arrive.

Wild spring weather continues to pummel various regions of the country. In Mississippi, Gov. Haley Barbour declared a state of emergency after an overnight tornado injured 20 people and damaged at least 60 homes.

But it's North Dakota's ominous weekend forecast that could be the most devastating.

VIDEO: Flood Fears Rise in Fargo, North Dakota Play

The worst of it is playing out in Fargo, where volunteers have thrown their hearts and hopes into constructing huge sandbag levees along a 12-mile stretch of river ahead of expected floods.

Tim Hogan and his nephew Jesse drove three hours to help.

"We've been working for two-and-a-half days and you really think you're doing something," Hogan told ABC News.

The National Weather Service predicted that the river could crest at as high as 43 feet by Saturday afternoon, far exceeding estimates and record levels set during the devastating floods of 1997.

"I think we're at the point where it's like, 'Bring it on,'" a sandbagging volunteer joked about the looming waters.

Bismarck Blasts to Unclog Ice-Jammed River

Near Bismarck, N.D., officials were breathing easier after the Missouri River dropped two feet after C-4 explosives were used to break up car-size blocks of ice that were clogging the river and sending water over the banks. The National Guard has determined that a third round of blasts won't be needed to break up what remains of the dangerous ice jam.

Huge chunks of ice started piling up on Monday at a bend in the Missouri River just south of Bismarck. The ice jam stretched half a mile wide at one point, disrupting the river's flow, causing the water to spill its banks. More than 1,700 people were forced to leave their homes.

"We had to relieve some of the backwater, which was threatening the people and property of Bismarck," said Eric Kelly, a member of the Advanced Explosives Demolition Inc.

Kelly's team, more accustomed to demolishing buildings than ice, was helicoptered in Wednesday afternoon to drill several dozen holes in the ice jam, filling each with two pounds of C-4 explosives.

On Wednesday, two explosions could be heard for miles as Advanced Explosives Demolition Inc. took on the dangerous and delicate operation to clear thousands of tons of rock-hard ice from the river. Overnight the river dropped two feet and is flowing again.

The National Guard said hundreds of homes near Bismarck have been flooded, but that number could have been in the thousands if officials had not acted quickly and aggressively.

Flooding is also a concern in South Dakota and Minnesota.

Tornado in Southeastern Mississippi

While residents were sleeping, a tornado with winds 150 miles an hour struck the town of Magee, Miss. Homes were shattered into pieces, trees toppled, cars were blasted with debris, and the devastation stretched for 17 miles, yet there were no reported deaths.

While the National Weather Service says warning sirens went off 10 to 20 minutes before the twister, they weren't heard on the town's outskirts, where Daniel Frierson and his young family slept.

"You heard the loud noise … [and] everything was on top of us," he told ABC News.

Frierson covered his 9-year-old son with his own body as the walls of their home came crashing down. Unbelievably, this is the second house Frierson has lost to mother nature.

"I know we lost a lot of stuff, I'm just grateful we survived," he said.

Down the road, the 100-year old Corinth Baptist Church was destroyed.

"Only the doors to its sanctuary were left standing," Katherine Gunby, spokeswoman for the Mississippi Emergency Management Agency, told The Associated Press.

Magee, just southeast of Jackson, was battling two to three inches of driving rain, when the tornado struck. The state's emergency management agency reported today that 20 patients have been transported to hospitals.

Residents Construct Sandbag Levees Ahead of Flooding

Meantime in Fargo, residents along the Red River are trying to shore up sandbag levees ahead of expected flooding.

Neighbors pitched in to make sure the homes of first responders, like Capt. Dave Todd of the Fargo Police Department, were safe from waters that already flooded his driveway.

"I was hoping that what we have done would hold," said Janet Iverson, a Fargo resident. "I noticed that the dike had fallen where the subpump was, so I filled some bags, about 20 of them, and threw them out the dining room windows."

"Everybody's got, you know, jobs to do too, while they're still trying to fight this thing," said Iverson's husband, Wade.

The cold weather isn't helping. The 30-pound sandbags typically fit together like puzzle pieces, but that changes when they freeze and become more rigid.

"If we leave them sitting outside for too long, they become like blocks of concrete and they're hard to work with, and they don't really work for flood protection at that point," said Capt. Dave Todd.

Thousands of volunteers from across the state worked around the clock Wednesday to hold back the water. Local universities and high schools canceled classes to lend manpower to the city for the sandbagging effort.

"They're in need of students and anyone else who can work," said Karl Underdahl, a college student. "We're here working."

Fargo Mayor Dennis Walaker said the city is bracing for the worst.

"We're talking about levels never reached before by any stretch of the imagination," he said.

A 43-foot crest in Fargo would be almost four feet higher than the record level of 39.6 in April 1997, when the area was struck by one of the largest and costliest floods in U.S. history. President Obama has already declared the state a federal disaster area.

"The water's coming up. The snow's coming down. The rain is coming down. … It's crazy," said Eric Lorenz, a sandbag volunteer who waded through six inches of snow.

Downstream from Fargo in Oxbow, the Missouri River showed its muscle when icy floods burst levees and swallowed homes. Rescuers in airboats pulled stranded residents to safety.

"It was terrifying," said one resident who was rescued by officials Wednesday. "The water wasn't that deep this morning and we woke up, we got to the window… and there was the river... just right there."

ABC News' Lauren Sher contributed to this report.