By Dennis Romero, Kalhan Rosenblatt and Phil Helsel
A massive winter storm created travel and commuting trouble for almost 200 million people in as many as 39 states Wednesday.
The system dumped rain, snow and ice across the South, Midwest, Mid-Atlantic and southern New England.
By 12:30 p.m. ET Wednesday, almost 2,000 flights had been canceled and more than 2,700 flights had been delayed, according to the flight tracking website FlightAware.
New York’s John F. Kennedy International Airport on Wednesday reported 316 canceled flight arrivals and departures; LaGuardia Airport had 255 cancellations; and Newark Liberty International Airport reported 205 canceled flights.
In Nebraska, several people were injured, including one with life-threatening injuries, after crashes involving nine semis and two passenger vehicles, and the weather played a role, the state patrol said.
Nine semis and two passenger vehicles were involved in multiple crashes on I-80 near mile marker 328 this morning just after 9:00.
There were multiple injuries. Our thoughts are with those affected.
Two tractor-trailers crashed and jackknifed on Interstate 80 in Hamilton County around 9 a.m. Wednesday, and other vehicles, including a Jeep Cherokee, were involved in a chain reaction crash. Then a pair of semis came upon that crash scene and were unable to stop and one struck the other, pushing it into the Jeep, the state patrol said.
A passenger in the Jeep, Jason Palmer, 29, of Indiana, was airlifted to a hospital in Kearney with life threatening injuries, according to the agency. The driver of the Jeep was treated and released, and a semi's driver also suffered non-life-threatening injuries, the state patrol said.
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Snow and a wintry mix is expected to hit the northern mid-Atlantic states and the Great Lakes and Northeast on Wednesday evening, and rain is expected across much of the Deep South through Friday evening, the National Weather Service said.
Flash flood watches stretched from western Tennessee and northern Mississippi to northern Georgia and in parts of West Virginia, and winter weather advisories or warnings covered a swath of the nation from northern Minnesota to Maine.
More than 10 inches of snow was reported in parts of Wisconsin and Minnesota, and the Minneapolis area saw more than 8 inches, according to the weather service. In parts of central and Pennsylvania, ice between 0.12 inches and 0.25 inches was reported Wednesday evening. Parts of Mississippi had gotten around 3 inches of rain over 24 hours as of Wednesday afternoon.
Parts of Connecticut, the New York City metro area and New Jersey were under a winter weather advisory through 6 a.m. Thursday, the agency said.
Even before the storm arrived Wednesday, officials were calling for caution. In New Jersey, Gov. Phil Murphy declared a state of emergency effective at 5 a.m. Wednesday. "We are urging residents of New Jersey to drive with caution and use their best judgment during this time," he said in a statement.
New York City's Emergency Management Department also issued an advisory. "We are expecting snow and sleet to develop in the afternoon, causing for a messy evening commute," emergency management commissioner Joseph Esposito said in a statement. "We advise you to use mass transit, give yourself extra travel time and exercise caution."
Pennsylvania Gov. Tom Wolf urged motorists to stay home. "This storm could bring with it a travel mess, and so I encourage everyone who can stay off the roads to do so tomorrow." All Philadelphia public schools were closed Wednesday.
The state's Department of Transportation issued a commercial vehicle ban for certain roads that was to last "through the storm," according to a statement.
The sub-freezing temperatures also prompted preparations for the homeless.
In Newark, New Jersey, Mayor Ras J. Baraka announced the activation of a "Code Blue" alert that signals sub-freezing temperatures and the opening of emergency shelters. In Washington, city officials declared a "cold emergency" and asked residents to report homeless people in need of shelter.
In the snowy Midwest, the roads proved treacherous for drivers.
The Nebraska State Patrol said Wednesday afternoon that in the last 24 hours, troopers responded to 30 crashes, including the large one involving tractor-trailers near Aurora, and 166 calls to assist motorists, and other calls. The total number of weather-related events handled by the patrol was more than 200, the agency said.
The Minnesota State Patrol tweeted that it responded to 140 crashes from 10 a.m. to 4 p.m. Wednesday, 16 of which involved injuries but none of which were serious. It said 216 vehicles spun out or went off the road, and three semis jackknifed. It urged people to slow down and increase following distances.
Although hundreds of flights were canceled Wednesday, the travel headache caused by the storm had already affected air travelers Tuesday.
American Airlines issued a "travel alert" and canceled 280 flights, mostly involving smaller aircraft that use regional airports, scheduled for Wednesday.
Southwest Airlines warned in a statement of delayed, diverted or canceled flights in the Ohio Valley and in the Northeast on Wednesday. Travelers using airports in Baltimore, Boston, Cleveland, New York, Philadelphia and Washington could be affected, the airline said.
And in Washington, Ronald Reagan National Airport appeared to suggest that travelers think twice about flying at all. "Several airlines have waived change fees for customers wishing to proactively rebook their flight to avoid tomorrow’s winter storm," the airport tweeted.
"Travel anymore is not easy, so you expect the unexpected," Stacy Flye, who was trying to get home from Reagan airport to Florida, told the Associated Press. "And you know, we knew the weather was going to be bad, but sometimes you just have to take your chances."
Dennis Romero writes for NBC News and is based in Los Angeles.
Kalhan Rosenblatt is a reporter for NBC News, based in New York.