(CNN) - Heavy flooding continued in Nebraska on Friday as it and other states in the Midwest geared up for days and even weeks of water-logged misery.
"As snow and rain pass, many communities have experienced devastating flooding. This could last for quite some time," Nebraska Gov. Pete Ricketts said.
At least 37 people were rescued from flood waters Thursday and rescues continued Friday, said Nebraska National Guard Adjutant General Daryl L. Bohac during an afternoon briefing. No fatalities have yet been reported.
Nebraska and other parts of the Midwest are coping with heavy flooding this weekend in the wake of a powerful "bomb cyclone" as well as from the natural snow melt during spring thaw, forecasters said.
Communities in that state as well as others in Iowa and South Dakota remain under a flood warning for rain and snow melt.
"Nebraskans should watch the weather and waterways in their communities closely in the coming days, and be prepared for historic levels of flooding even if it has not hit their community yet," Ricketts said. " As Nebraskans know, conditions can change quickly, and everyone needs to be prepared."
Omaha Mayor Jean Stothert declared a state of emergency Friday for the city. The Omaha Papillion Creek Wastewater Treatment Plant shut down Friday because of the flooding, according to a release from the city, and power to the plant has been cut off.
Historic floods draw comparisons to 2011
Bohac stated that in some ways, the flooding being seen across Nebraska is more dangerous than historic flooding the state experienced in 2011.
"If you think about to 2011, just to give you a contrast, the National Guard operations were putting soldiers and airmen on the levees to monitor their stability and other issues. We did not run one rescue operation in that flood," Bohac said. "This is a different environment than we experienced in 2011. More complex and in some ways more dangerous."
The 2011 summer flood left five dead, caused more than $2 billion dollars in damage and flooded out 4,000 homes, according to CNN affiliate WOWT-TV. The flood of 2011 spanned the entire summer, WOWT reported, causing problems all along the Missouri River.
Omaha Fire Chief Dan Olsen said the Nebraska National Guard has deployed Black Hawk helicopters to a couple of rescues across the state. Chief Olsen said multiple pieces of equipment, boats, helicopters, large vehicles and even tractors are being used to navigate flooded roads. Along with aerial support from the National Guard, Chief Olsen urged residents who are told to evacuate to leave their homes, and not to wait before it's too late.
Omaha rescue crews have transported several people suffering from hypothermia as a result of the flooding, Olsen said.
Olsen also said that while there are dive team members on standby and other emergency rescue members are being deployed "into very serious and dangerous waters," they can only do so much.
"There comes a point where it's very possible, although we'll do our absolute best and risk our all to try to get to you, there may be instances where it's just not possible for us to do that," he said.
Levees fail and nuclear plant prepares to shut down
The Nebraska Emergency Management Agency opened a State Emergency Operation Center after an emergency declaration on Tuesday in response to the flooding and blizzards.
Omaha, which expects the Missouri River to crest at 33.7 feet on Sunday, has been working to make sure the city is protected.
"Omaha has 13 miles of flood control on the Missouri River. The levee is safe and the river is not expected to compromise the levee. The levee is being monitored as a precaution," Mayor Jean Stothert said Thursday.
The Cooper Nuclear Station near Brownville, about 80 miles south of Omaha, is taking additional precautions to ensure safety at the plant, Mark Becker, spokesman for the Nebraska Public Power District told CNN.
The plant issued a notice to the Nuclear Regulatory Commission Friday morning of an unusual event as the water levels along the Missouri River reached the procedural limit.
Becker expects the water to rise another foot or so, and at that point additional safety precautions will be put in place like sandbagging doorways to protect equipment. The plant has already placed sandbags in key external sites.
The National Weather Service predicts the Missouri River will crest at 2 a.m. Saturday morning, and if it reaches the predicted level the reactor will shut down at the power plant. Becker told CNN personnel will remain at the plant to ensure safety.
"We've had a very cold winter, the ground is frozen, there's currently between 8 inches to a foot of snow melting, followed by rains and additional snow. A lot of rivers in Nebraska are flooding, which is creating this issue," Becker said.
Olsen said "rescues are ongoing" in the area, including National Guard helicopter missions, and some evacuees have been transported to the hospital.
Olsen and other authorities who briefed reporters at the Douglas County Emergency Management office are concerned that people staying in their homes too long may be difficult to evacuate.
Earlier, a levee failure in east-central Nebraska spurred a flash flood emergency as forecasters urged citizens to '"move to higher ground now."
The emergency is for areas around Valley, west of Omaha, between the Platte and Elkhorn rivers after a levee failed on the Union Dike, the National Weather Service said.
The Omaha-Valley weather service office said it was evacuating its personnel.
"This is an extremely dangerous and life-threatening situation," the weather service said. "Do not attempt to travel unless you are fleeing an area subject to flooding or under an evacuation order."
Nebraska Game and Parks Commission employees used a fan boat to rescue residents in Gretna. The Mead Fire Department was helping people near Horseshoe Lake. The Columbus Police Department warned residents to stay away from the Black Bridge. One person is believed to be missing in Boyd County when a dam collapsed and a house was washed downstream.
State of emergency declared in Wisconsin
Wisconsin Gov. Tony Evers declared a state of emergency due to statewide flooding.
"Rapid snowmelt and rain have caused flooding that has impacted homes, businesses, and cities and towns across Wisconsin," Evers said in a tweet. "Today I declared a State of Emergency to provide additional personnel and resources as needed to assist in emergency response and recovery operations."
About 300 people have been evacuated in Wisconsin, Lori Getter of the Wisconsin Emergency Management told CNN. No fatalities have been reported.
Southern Wisconsin towns battled high waters and a flood warning in effect till Saturday morning. The region is experiencing road closings as a result of flooding caused by the snow melt, rainfall, frozen ground and ice jams, the weather service said.
In Fond du Lac, flooding was occurring on the Fond du Lac River due to an ice jam, forecasters said, while other areas affected included Lodi in Columbia County, Darlington in Lafayette County, Prairie du Sac in Sauk County and DeForest in Dane County.
"Things have calmed down, we still have some flooding going on, but rivers are leveling up and water is receding," Getter said.
The problem with the snow, Getter said, is that when it melts the water has nowhere to go.
"This is going to take a while to clean because winter or spring flooding is different from any other flooding. We still have to keep an eye on the snow that continues to melt," Getter said.
'Bomb cyclone' heads north to Canada
The intense bomb cyclone that brought blizzard conditions to the region was moving into Canada on Friday.
Dangerous weather conditions were expected for millions who are under some sort of watch, warning or advisory as it heads east and then north.
A bomb cyclone occurs when there is a rapid pressure drop, with a decrease of at least 24 millibars -- a measure of atmospheric pressure -- over 24 hours. This storm dropped 33 millibars from Tuesday into Wednesday.
"Although the focus of the bomb cyclone was clearly on the blizzard side, the area east of the low picked up significantly heavy rains on top of existing snowpack and frozen ground that was unable to absorb any of the rain and water runoff," CNN meteorologist Chad Myers said.