FARGO, N.D. -- As the Red River rises into "uncharted territory," officials Thursday pleaded for thousands of volunteer sandbaggers, readied their evacuation plans, and vowed to build the dikes a foot higher than planned in an effort to hold back the water.
After days of predicting the Red River would crest between 39 and 41 feet, the National Weather Service settled on the higher number Wednesday - raising new concern among residents.
Mayor Dennis Walaker described 41 feet as "uncharted territory," noting the Red's record high at Fargo was 40.1 feet in 1897. Walaker said he was still confident the city would beat the flood, but that contingency plans were needed.
"We're into the contingency dikes now, and what they are is a secondary dike to protect the city in case the first line of defense fails," Walaker told the CBS "Early Show" Thursday morning.
Officials said they would build their dikes a foot higher than planned, to 43 feet. The city also said it would distribute evacuation information to residents on Thursday - just in case. The river was projected to crest on Saturday afternoon.
Police Chief Keith Ternes urged people with disabilities to consider leaving the city, saying: "If they expect us to get to them and get them out, they should give serious consideration." Hospital officials were also identifying patients that might need to be moved early.
Officials in Fargo and neighboring Moorhead, Minn., put out another call for volunteers. Fargo requested more than 2,000 volunteers to complete sandbag dikes.
To the west, officials in Bismarck were battling ice jams in the Missouri River. Demolition crews blasted chunks of ice Wednesday in a bid to open a channel, like pulling out a giant plug to drain a flood threatening the city. Officials planned two more rounds of explosives.
"We are cautiously optimistic," Bismarck Mayor John Warford said after explosives detonated on about 500 feet of ice just south of the jam.
Water backing up behind the dam of car-size ice blocks already had forced the evacuation of about 1,700 people from low-lying areas in North Dakota's capital city. Fox Island, which has several dozen upscale homes, was flooded.
Gov. John Hoeven said the first demolition round, "blew a large chunk" of ice out of the river.
"Right away, you could see water moving, as well as ice and trees that were in the water," he said. "Clearly, they are moving water through the ice jam now."
The Missouri River jam was created by ice floating down the Heart River, with some chunks up to 3 feet thick and the size of small cars. The jam was about 11 miles downstream from the city.
"The ice is just solid as a rock," Assistant Water Commission Engineer Todd Sando said.
Crews from Advanced Explosives Demolition, with help from National Guard, the Army Corps of Engineers and the Coast Guard, drilled 80 holes in the ice to detonate clay-like explosives. Greg Wilz, the state's homeland security director, said salt would be used to help speed the breakup and officials were considering backhoes to break up ice sheets near the river's west bank.
Roger Kay, an Army Corps of Engineers hydraulic engineer, said ice downstream from that jam appeared to be melting and weakening, meaning less resistance once the jam is broken loose.
"The ice is showing signs of becoming more rotten," Kay said.
A second ice jam about 10 miles upstream of Bismarck was also a concern, holding back a growing reservoir.
The National Weather Service posted a flash flood warning for a three-county area, saying the integrity of that ice jam, in an area called Double Ditch, was unpredictable.
Residents of low-lying subdivisions in Bismarck and neighboring Mandan had been told to evacuate.
President Barack Obama declared the entire state of North Dakota a disaster area late Tuesday in response to widespread flooding. The Minot Air Force Base was deploying two rescue helicopters to Bismarck, in case people need to be saved from floodwaters.
Mike Hall, who is in charge of the Federal Emergency Management Agency's North Dakota response to the flood, said the agency is shipping almost 20,000 meals, 4,500 blankets and hundreds of toiletry kits to the Grand Forks Air Force Base. From there, the supplies will be distributed as needed, Hall said.
More sandbagging was planned in part of Grand Forks, the city hardest hit by the 1997 Red River flood. An elaborate dike system was built after that disaster. The Red rose to 42.5 feet in Grand Forks by midday Wednesday with a crest near 52 feet projected for Monday. The record there was 54.4 feet, set in 1997.
Snow fell Wednesday in the Red River Valley region - and continued to fall into the night. Several inches were already on the ground, and the National Weather Service said 2 to 4 more inches are expected in Bismarck on Thursday, while up to 1 inch is expected in Fargo.
Associated Press writers James MacPherson, Blake Nicholson and Dale Wetzel in Bismarck and Dave Kolpack in Fargo contributed to this report.