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(CNN) -- A massive winter storm spanning 20 states dumped more than a foot of snow in some places Thursday and brought life to a standstill in parts of the central United States.
About 60 million people -- 20% of the U.S. population -- were under winter weather warnings, watches and advisories in the 750,000 square miles affected.
Statewide emergency declared
Missouri Gov. Jay Nixon declared a state of emergency. Snow, sleet and ice could wreak havoc, and parts of the state could see more than 10 inches of snow.
Kansas City, Missouri, Mayor Sly James also declared a state of emergency. There were 250 snow plows working to clear roads in the city, and residents were urged to limit travel.
Kansas City International Airport shut down because of the weather, according to Joe McBride with the city's aviation department.
The city picked up 7.6 inches of snow, a record daily snowfall, the National Weather Service said.
CNN iReporter Joseph Kopel posted photos of empty shelves in St. Joseph, Missouri, on Wednesday as people stocked up for the blizzard.
Authorities in Kansas had closed a 240-mile stretch of Interstate 70 west of Salina earlier in the day. Two dozen soldiers from the Kansas National Guard later searched the interstate and U.S. Highways 54 and 400 farther south for any stranded travelers.
In Wichita, despite crews spreading salt and sand across roads for days, many roads remained slick. Side streets were worse, CNN affiliate KSN reported.
Gov. Sam Brownback called for people to stay home.
"If you don't have to travel, don't do it," the governor said.
The storm started to wind down Thursday night in Wichita after leaving 14.2 inches of snow over two days -- the second highest storm total in the city's history, according to the National Weather Service.
Topeka received 9.2 inches of snow.
The University of Kansas closed two of its campuses -- in Lawrence and Overland Park, both near Kansas City -- through Friday because of the weather.
Across the country, flights were canceled or delayed because of weather. St. Louis, Dallas/Fort Worth, Chicago's O'Hare, and Denver had the most cancellations and delays after Kansas City, according to FlightStats, which tracks air travel.
United Airlines announced Thursday that certain affected travelers can change their itineraries without paying fees.
Some drought relief expected
There is a silver lining for some areas facing the heavy snowfall.
"Big chunks of Nebraska, Kansas, Oklahoma and Texas" are facing exceptional drought, HLN meteorologist Bob Van Dillen said. "You squeeze out the water from the melting snow, and you're talking 1 to 2 inches of water for those dry regions."
Wednesday, CNN iReporter Doug Simonton in Tulsa, Oklahoma, posted a photo of a car covered in snow and said numerous traffic accidents had been reported around town.
A large system
The storm system is huge and carries with it a warmer, wetter Southern component.
It will eventually stretch from the Dakotas to Houston, Myers said. While it will remain snowy in the north, the system was forecast to spawn torrential rains and tornadoes along the Gulf Coast and dump freezing rain over Arkansas and Missouri.
"There's going to be a monster ice storm over Springfield and Branson, Missouri. Think of an inch of ice coating everything," Myers said. "Power lines will be coming down. Trees will be coming down."
In St. Louis, freezing rain is predicted to fall on top of a thin layer of snow, which will have "a significant impact on travel," the National Weather Service warned.
North of where the most snow will fall, Chicago could receive as much as 6 inches, CNN's Sarah Dillingham said. The city is running 15 inches below its average snowfall for the season.
Severe thunderstorms moving in from the Gulf of Mexico are expected to bring 2 to 6 inches of rain to New Orleans and Montgomery, Alabama, according to CNN's weather center, before rolling up toward Atlanta.
The torrential rains could lead to significant river flooding, as flood watches are still in effect from last week's heavy rains.
Heavy winds, hail and tornadoes are possible, the National Weather Service said. Downpours are expected to continue into Friday.
Desert dwellers stunned
On Wednesday, the winter storm system left a rare thin layer of snow across the deserts of Arizona, New Mexico and southern California as far south as the border with Mexico.
"I've been here for over 10 years and I've never seen it snow like this," Kayla Avery of Tucson, Arizona, said in a CNN iReport, which came with a video of the snowfall.
"There is more snow on the ground in Tucson today than I have seen in over 30 years living here," Carrie Tucker said in another iReport.
Mona Jensen of Dolan Springs, Arizona, posted photos of her 8-acre property blanketed by snow.
Katie June in Yucca Valley, California, shared a shot of a snow-covered cactus.
"Some of the larger ones are having a hard time," she wrote. "But they all enjoy the drink!"
Joan Dedmon in Tuscon, Arizona, also found snow on cacti and shared a picture of a snow-covered birdfeeder. She said it confused the hummingbirds who were trying to get a meal before dark.
CNN's Steve Almasy, Mike Pearson and Pedram Javaheri contributed to this report.