From left, Cody Stensgard, Michael Stensgard, Jack Lubka and Andy Drabbs struggle in the snow to unload a boat full of sandbags at the Stensgard home as the Red River rises Wednesday in Fargo, N.D. (Carolyn Kaster/Associated Press)

A bleak outlook for Fargo, N.D., grew more ominous Thursday evening, as officials twice raised their forecast of how high the swollen Red River will crest in the next few days.

Early Wednesday, U.S. President Barack Obama declared the state a federal disaster zone, meaning Washington will pick up 75 per cent of state and local government costs to fight the flood.

At the time, the National Weather Service had been predicting the river would crest at 12.4 metres on Saturday afternoon, a level that Fargo Mayor Dennis Walaker described as "uncharted territory."

After a day of snow and rain in the area, on Thursday, that prediction was increased to just under 12.5 metres, causing an urgent renewal of sandbagging efforts.

But the National Weather Service later revised that estimate, saying in an advisory issued late Thursday afternoon that the Red was expected to crest between 12.5 and 12.8 metres but could reach 13.1 metres. It said water levels could remain high for up to a week — a lengthy test of on-the-fly flood control.

The Red River's record high in Fargo was 12.1 metres in 1897.

Tim Corwin, 55, whose south Fargo home was sheltered by sandbags up to about 13 metres, said he wasn't giving up but was pessimistic after hearing the new potential crest.

"I've lived here 40 years, and over a 30-minute span, I've reached a point where I'm preparing to evacuate and expect never to sleep in my house again," he said.

Communities evacuated

Later Thursday, officials ordered the evacuation of one Fargo neighbourhood and a nursing home after authorities found cracks in an earthen levee.

Residents were not in immediate danger, and water was not flowing over the levee, Mayor Dennis Walaker said Thursday night.

The evacuation was being enforced as a precaution.

Officers were going door to door to the roughly 40 homes in the River Vili neighbourhood and were evacuating Riverview Estates nursing home. The number of residents at the nursing home wasn't immediately clear.

Authorities across the river in Moorhead, Minn., also stepped up evacuations Thursday. They recommended that residents in the southwest corner of the city and in a northern area called Oakport Township leave.

Race against time

North Dakota National Guard troops shore up a dike during a snowstorm along the rising Red River behind the Shriners Center on Wednesday in Fargo, N.D. (Jim Mone/Associated Press)

With 800 soldiers dispatched to the city to build protective dikes out of 1.8 million sandbags, "the city feels comfortable enough sandbags are being produced," Col. Jim Hrdlicka of the U.S. National Guard told CBC News.

Authorities are making more than 500,000 sandbags per day in a desperate attempt to build up the dikes surrounding the city to an unprecedented height of 13 metres.

But there are concerns the river could be backed up all the way north to Winnipeg as early as this weekend. Evacuation plans are being crafted in case of emergency.

"Are we confident we're going to beat this? Yes we are," said city commissioner Tim Mahoney.

Residents remained equally optimistic.

"We'll do the best we can and see what the Lord does. Maybe he'll hold back the flood," said Chuck Perkins.

Demolition crews called in to destroy ice jams

Meanwhile, ice jams have formed along the Missouri River, with dangerous volumes of water pooling behind them.

Emergency officials attempted to blast through a jam about 17 kilometres downstream from the city of Bismarck.

Demolition crews were flown to the area by helicopter to drill holes in the ice and lay down explosives. The crews were tethered for their safety, with two boats on standby during the dangerous work.

"We are cautiously optimistic," Bismarck Mayor John Warford said.

A second ice jam has formed about 16 kilometres upstream from Bismarck.

Evacuations ordered

Elsie, one of the two Stensgard family dogs, stands on the earthen and sandbag dike surrounding the Stensgard home, not pictured, which overlooks a flooded outbuilding as the Red River continues to rise on Wednesday in Fargo, N.D. (Carolyn Kaster/Associated Press)

While emergency crews worked on the jam, about 1,700 people were ordered out of low-lying areas nearby for fear of major flooding.

"We just grabbed a bag, threw some stuff in and left," said Jane Pole of Fox Island.

The U.S. National Weather Service posted a flash-flood warning for three counties, saying the integrity of the second jam is unpredictable.

The Army Corps of Engineers cut water releases from the Garrison Dam to ease the flooding, which also meant a cut in power generation at the dam.

People in nearby communities fear the flooding may prove to be as disastrous as in 1997, when tens of thousands of people were forced to flee their homes in North Dakota, Minnesota and southern Manitoba. In the United States, 11 people died as a result of the 1997 flood, which caused an estimated $4.1 billion US in damages.

The river has been swollen by heavy winter snowfall and an early freeze that locked moisture into the soil.

With files from the Associated Press