National Weather Service meteorologists warned the storm could bring potentially "life threatening" and "crippling" blizzard conditions portions of southeast Kansas, northwest Oklahoma and the Texas panhandle.
Amarillo, Texas, reported 11 inches of snow early Monday and the National Guard was called to help the Texas Department of Public Safety deal with stranded motorists, the Amarillo Globe-News reported on its website.
The National Weather Service posted the message "Do not travel" on its website as snow fell at 2 to 3 inches per hour with high winds, making it impossible for drivers to see. City officials said snowplows had been pulled off the roads for safety concerns. The weather service virtually begged people to stay home during what it called "a crippling, historic blizzard." Snowdrifts of 4 to 6 feet were possible in places, forecasters said.
A Federal Aviation Administration website said Rick Husband Airport in Amarillo would likely remain closed until 5 a.m. Tuesday. Dallas-Fort Worth Airport was experiencing 2 1/2-hour delays due to the high winds.
The Transportation Department closed portions of westbound Interstate 40 from near Amarillo to Albuquerque. The Texas Department of Public Safety shut down portions of U.S. highways 87 and 187 because of whiteout conditions that were expected to remain through Monday afternoon.
Across Oklahoma and the Texas panhandle, school districts, senior centers and churches were closed until at least Tuesday, as were some state and local offices.
In Oklahoma, the state's two major colleges planned to close: Oklahoma State in Stillwater was shut down at 12:30 p.m. Oklahoma University in Norman was to close at 1:30 p.m.
Roads throughout the Oklahoma panhandle were closed due to whiteout conditions, The (Oklahoma City) Oklahoman said.
In Kansas, which received more than a foot of snow in some places in last week's storm, Gov. Sam Brownback extended a state of emergency declaration to include the new storm.
"This storm has the potential to be more dangerous than last week's storm," Brownback told Kansans late Sunday. "So, we ask you to stay off the road unless it's absolutely critical. If you have to be out, be prepared with a charged cellphone, an emergency kit with food, water, blankets, flares and a shovel."
Wichita, Kan., which got more than 14 inches Thursday, bringing the city to a virtual standstill, reported near-zero visibility Monday.
"It would have been nice if we'd had a few days to recover, to do some equipment rehab," Public Works Deputy Director Joe Pajor told The Wichita Eagle.
The snow began in late morning and driving conditions were characterized as hazardous. More than a foot of snow was predicted.
Forecasters predicted 8 to 10 inches of snow in northwestern Oklahoma after temperatures had reached the mid-60s Sunday, CNN said.
"May see 4-6 foot drifts! Traveling is beyond discouraged!" Rick Smith, warning coordination meteorologist for the National Weather Service in Norman, Okla., posted on Twitter.
With more than 9 inches of snow reported in some areas of Denver early Monday, airline operations were trying to return to normal after more than 200 flights were canceled and hundreds flights delayed because of the weather Sunday, the FAA said.
As much as 19 inches of snow were reported in Jefferson, about 70 miles southwest of Denver. The foothills west of Denver received nearly 2 feet by late Sunday, the weather service said.
A huge swath of the nation -- including Chicago, where 3 to 5 inches of snow and sleet were expected Tuesday -- prepared for snow and rain.
In San Antonio and Junction, Texas, the storm that brought snow farther north produced damaging winds, hail and an isolated tornado as thunderstorms race eastward to Houston and Lake Charles, La.
Other tornadoes were possible in Louisiana, Mississippi, Alabama, the Florida Panhandle and Georgia, the weather service said.
Some areas from Louisiana to South Carolina could get a possible 4 inches of rain. Mobile, Ala., expected heavy rains and wind gusts as strong as 30 mph, forecasters said.
Flood watches were in effect through Tuesday morning.