A powerful system of storms churned across the Rocky Mountains and into the Midwest on Wednesday, dumping snow, driving high winds and leaving tens of millions of people in its projected path.
Blizzard conditions were expected in parts of Colorado, Kansas and Nebraska, the National Weather Service said.
Denver was covered in 5 inches of snow Wednesday afternoon, and authorities said high winds caused crashes and road closures in western Colorado, The Associated Press reported. Airlines canceled 50 flights at Denver's airport, according to NBC affiliate KUSA.
In Chicago, the Illinois Emergency Management Agency (IEMA) issued an alert encouraging residents to stay aware of local forecasts and "be prepared to act quickly if storm warnings are issued."
"It's a huge, typical November storm," Weather Channel lead forecaster Kevin Roth said. "Winter is on the way, that's for sure."
The snowstorm that hit Denver was expected to continue into the western Plains," Roth said, with many areas seeing their first proper snow of this winter.
"Blizzard conditions will affect northeast Colorado, northwest Kansas and southwest Nebraska but Denver should escape," he said.
Winds could reach 35 mph, resulting in areas of blowing and drifting snow, the National Weather Service said.
NOAA's Storm Prediction Center has issued a tornado watch effective until 6 p.m. CST for parts of southeast Nebraska, southern and central Iowa, northern Missouri and northeast Kansas, The Weather Channel reported. That includes Kansas City, Des Moines and Omaha.
Chicago is likely to see thunderstorms and gusty winds but should escape the tornado threat, Roth said, but Kansas City was "not completely out of the woods."
"Severe thunderstorms and tornadoes can happen any time of the year," IEMA director James K. Joseph said in a statement, NBC Chicago reported. "We're keeping an eye on the storm system predicted for Wednesday, and encourage everyone to stay aware and be prepared to seek shelter if a storm warning is issued."
By late Wednesday, the snow is likely to have spread to St Louis, parts of western Illinois and as far as western Tennessee.
The most severe thunderstorms were likely in northeast Colorado, southeast Nebraska and northwest Kansas. Parts of Iowa could see both thunderstorms and snow, Roth said.
"November has a history of producing some significant weather events. We will have to keep an eye on things," Greg Carbin, warning coordination meteorologist at the Storm Prediction Center in Norman, Oklahoma, told The Associated Press.
Wet, heavy snow fell in Nevada on Tuesday, shuttering schools in Reno and knocking out power to thousands before moving eastward.
At Pi Kappa Cino Coffee in Sterling, Colorado, workers were checking their heaters and stocking up on coffee to handle a busy morning on the first significant snowfall of the season. "We always try to keep prepared for the winter, keeping extra water on hand and checking the heaters," owner Patricia Prescott said. "Business normally picks up because everyone wants our warm drinks."