The Associated Press . Barns are surrounded by the flooded Musselshell River west of Harlowton, Mont., on Thursday. Regional rains are forcing releases from dams that promise to swell the Missouri River past its banks.
LODGE GRASS, Mont. -- Rain-swollen rivers that have swamped Montana towns could keep flooding the region for another month or more as melting mountain snow delivers a second slug of water to the soggy Northern Plains.
Heavy rains are forecast through the holiday weekend. Warm weather after that is expected to kick off the melt of high-elevation snows that are much deeper than average.
Even with rivers running wildly from record rainfalls, agencies have started dumping massive volumes of water from low-land reservoirs to get ready for the annual spring melt. That's predicted to flood homes downstream in the Dakotas, and possibly in Iowa, Nebraska, Kansas and Missouri as well.
''There is going to be record flooding all along the Missouri River,'' said Paul Johnson, director of the Douglas County, Neb., Emergency Management Agency. ''This isn't going to return to normal anytime soon.''
In Montana, the state's famous rivers and streams -- swollen to several times their usual size in places -- continued to carry a torrent of debris and damage through small towns and over roads Friday as emergency officials brought in reinforcements and the governor toured the hardest-hit areas.
Mountain peaks were packed with up to twice as much melting snow as usual. And more rain was forecast for a Memorial Day weekend that will to be hard on travellers: Dozens of roads and highways were closed around the state as cresting waters broke through barriers and filled many homes with muddy floodwater.
Officials warned that dozens of campgrounds and fishing access sites also would be closed.
''We are going to be in floods not just here but all over Montana for the next 30 days,'' Gov. Brian Schweitzer said after a helicopter tour of the waterlogged Crow Indian Reservation south of Billings.
The U.S. Army Corps of Engineers said it had no choice but to continue record releases from brimming reservoirs. Dams built decades ago to contain dangerous floodwaters were now being used to release a carefully controlled torrent.
In Missouri and Nebraska, the river was already spilling over its banks and soaking low-lying farmland. More flooding was predicted as releases from swollen upstream reservoirs were expected to reach ''historic'' levels, officials said.
''We have gotten about a year's worth of rain in Montana in the last month,'' said Monique Farmer, spokeswoman for the corps' Omaha, Neb., district. ''It's just crazy. It's been an unusual year.''
Officials said water is encroaching on cities such as Fort Calhoun, Neb., and Sloan, Iowa -- where residents built a temporary levee out of sandbags to help protect a dozen homes near the river.
The Army Corps of Engineers predicted 2011 could be one of the wettest years on record in the Missouri River basin. The agency has predicted flooding into July.