CNN  — 

A fast-moving winter storm will unload a messy mix of heavy snow, strong winds and frigid temperatures across parts of the Midwest and Northeast over the weekend.

More than 100 million people are under some form of winter storm watch, warning or advisory from Missouri to Maine.

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Snow was piling up Saturday morning in Chicago, Detroit and Cleveland. Chicago could see 9 inches of snow by midday, the National Weather Service said.

Indianapolis was to get a messy mix of rain, snow and freezing rain Saturday morning, but it was expected to turn into snow by afternoon.

Cities on the storm’s southern edge such as Houston, Memphis, Tennessee, and Jackson, Mississippi, woke up to thunder and lightning Saturday.

As the storm quickly pushes east, forecasters expect a substantial amount of precipitation Saturday evening through Sunday up and down the East Coast.

A mix of snow and sleet will begin Saturday afternoon in New York and Philadelphia but shift to rain overnight. Boston will start with snow in the afternoon, followed by snow, ice and rain overnight through Sunday.

Inland areas of the Northeast and New England will likely see the most accumulation, with up to 2 feet of snow possible.

New York Gov. Andrew Cuomo said a ban on tractor-trailers and buses on most highways in the state will start at 3 p.m. ET Saturday.

Amtrak said it will operate a modified service Saturday and Sunday due to the weather.

Flights canceled

Travel will be affected through Sunday, with more than 2,700 flights involving domestic airports canceled, according to the flight-tracking site Airlines are issuing waivers for travelers in the Midwest and Northeast.

Eppley Airfield in Omaha, Nebraska, closed for several hours Friday after a Southwest Airlines flight went off a runway while taxiing. The plane slid onto a runway overrun area, Southwest said.

No one on board a Southwest Airlines flight was injured Friday at Eppley Airfield in Omaha, Nebraska.

None of the 150 passengers and six crew members was injured, it said.

Significant icing event is possible along I-95 corridor through New England

As the low tracks farther east, warm air is likely to mix in from the South. At this time, it’s uncertain exactly where the line between rain and snow will form.

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New Jersey Gov. Phil Murphy declared a state of emergency beginning at noon Saturday. He told residents to stay off the roads and prepare for possible power outages.

Severe storms possible in the South

More than 10 million people face a slight risk of severe weather Saturday in the South. The potential for dangerous weather stretches from Louisiana to Florida and north to Tennessee.

The main threats are damaging winds and isolated tornadoes.

A tornado watch is in effect for parts of Louisiana and Mississippi through Saturday morning, meaning conditions are favorable for a tornado to develop.

A flash freeze is likely behind the storm

Behind this second storm, a deep chill will grip much of the eastern half of the United States.

Temperatures are expected to drop so fast in some areas that any moisture on the ground or surrounding objects would likely freeze.

Highs on Sunday in the Kansas City area – where the Chiefs will host the New England Patriots in the AFC Championship game – will be in the twenties.

The extreme cold follows the storm and moves into the rest of the Eastern United States on Monday.

Monday’s forecasted high in Boston is 11 degrees Fahrenheit, and New York City will top out at 14 F. The Massachusetts Emergency Management Agency is warning residents the wind chill could drop as low as 20 degrees below zero early Monday.

This arctic air will spill out across the country later next week as far south as Florida, leaving most of the continental United States with below-average temperatures.

CNN’s Steve Almasy, Rob Frehse, Joe Sutton and Monica Garrett contributed to this report.