Powerful winter storm hits eastern half of the US

More than 5 million people across portions of Texas, Arkansas, Louisiana, Tennessee and Mississippi are under a tornado watch as intense thunderstorms rumble across the South Friday morning.

The tornado watch is in effect until 11 a.m. CT and includes Little Rock, Arkansas, Shreveport, Louisiana, and Jackson, Mississippi.

Thunderstorms stretch from the Texas Gulf Coast as far north as Illinois and Indiana early Friday morning.

But the greatest risk for these storms to turn severe and unload damaging winds, hail and tornadoes is over the Lower Mississippi Valley, where a Level 3 out of 5 risk for severe thunderstorms is in place.

Another bout of rain will fall on the already-soaked Northeast on Friday, threatening to trigger disruptive and damaging coastal flooding in several of the region's major cities through Saturday.

More than 7 million people are under coastal flood warnings along swaths of the Northeast, including residents of Philadelphia and parts of New York, where Nassau and Suffolk Counties could be overwhelmed with up to 3 feet of coastline flooding.

"This will result in extensive road closures and flooding of low-lying property including parking lots, parks, lawns and first floors and basements of homes/businesses near the waterfront," the National Weather Service in New York warned. "Vehicles parked in vulnerable areas near the waterfront will likely become flooded and/or submerged."

In New York City, where a coastal advisory is in place, 1 to 2 feet of water could inundate ground-level areas. 

About 35 million people -- stretching from North Carolina to eastern Massachusetts -- are under flood watches Friday as the storm pushes through the eastern US.

More than 50 million people are under a severe storm threat across the Southeast on Friday after overnight storms brought high winds and almost a dozen reports of large hail in the South.

Parts of northern Alabama and Mississippi are the most at-risk for severe weather, with the main threats being powerful winds, large hail and a chance of tornadoes.

A tornado watch is in effect until 5 a.m. ET for parts of western and central Arkansas, northwestern Louisiana, southeastern Oklahoma and northeast Texas.

Other major cities in the storm's path include New Orleans, Atlanta, Nashville, Tennessee, and Tampa, Florida. 

As winter weather sweeps the country, more than 1,170 flights have been canceled within, into or out of the United States so far today, according to tracker Flight Aware.

In Chicago, which is set to receive more than 8 inches of snow, O'Hare International Airport tops the charts with more than 400 flights canceled in and out of the travel hub. The city's other airport, Midway International, is also among the hardest-hit with more than 100 cancelations.

Other airports with a high number of cancelations include Denver International Airport in Colorado, Milwaukee Mitchell International Airport in Wisconsin and Newark Liberty International in New Jersey.

Here's what to do if your flight is canceled or delayed.

Here's a look at the snowfall and other conditions expected in some of the Midwestern cities in the storm's path. All times are local to the cities indicated.

Chicago

Des Moines

Grand Rapids

Milwaukee

Minneapolis

A powerful storm is set to unleash blizzard conditions, severe thunderstorms, damaging winds and brutal cold across the eastern half of the US in what will be a dangerous dose of déjà vu for many.

When staying indoors during cold temperatures or a winter storm, the US Centers for Disease Control and Prevention offers these tips:

And if you must go outside, the CDC and National Weather Service have some recommendations for staying safe while venturing outdoors during a winter storm,

Read more about how to stay safe during winter weather.

Iowa is one of the states where blizzard conditions are expected Friday -- and blizzard warnings will soon cover a majority of the Hawkeye State.

Pelting snow and winds are expected to create whiteout conditions and heavy snow accumulations. Widespread snowfall totals of 6 to 11 inches are expected in the state.

The warnings are set to be in place from 10 a.m. Friday to 6 a.m. Saturday CT and include the cities of Des Moines, Davenport, Waterloo, Ames, Sioux City and Cedar Rapids.

“Storms of this magnitude are fairly rare with recurrence around once or twice per decade,” the National Weather Service in Des Moines said. “Travel is not recommended except if absolutely necessary, especially by Friday afternoon into the evening.”

Severe thunderstorms that may produce dangerous tornadoes will threaten parts of the South overnight and into the daylight hours Friday morning.

Nighttime tornadoes are twice as likely to be deadly as those that occur during the day, a 2022 study found.

Researchers found that nighttime tornadoes from 1950 to 2019 made up less than a third of tornadoes, but were responsible for a staggering 42% of tornado deaths.

Tornado fatalities during the daytime hours have decreased by 20% since the late 1800s because of advances in science and communication, the study found. But the amount of nighttime tornado fatalities actually increased by 20% during the same period.

The increase could be due to factors like location and home construction, but the researchers said the most obvious issue is a large portion of the population is asleep at night and may miss life-saving warnings.

It’s difficult to spot a tornado at night, even for those who are awake or are awoken by warnings.

The best way to stay safe during a nocturnal tornado threat is to have multiple ways to receive severe weather warnings. At the very least, make sure emergency alerts are enabled on your smartphone. Charge devices ahead of time and set phones or alarms on a loud volume so you're not caught unaware.

Significant snow is on the way for the greater Chicago area, but totals will vary wildly from an inch or two to closer to double-digits depending on where you are. 

“We are expecting a tight gradient in snow across a few miles inland from Lake Michigan,” Brett Borchardt, a meteorologist with the National Weather Service in Chicago, told CNN.  

Meaning parts of Chicago close to the lakeshore are likely going to end up with significantly lower snowfall totals than those in the western suburbs Friday through Saturday.  

This difference is tied back to the warmth of Lake Michigan, according to Borchardt. 

Water temperatures on the surface of Lake Michigan are currently higher than they’ve been since records began in 1995, according to data from NOAA. Because of this warmth, the total percentage of the lake covered in ice is hovering near-zero. At this point in January, at least 10% to 20% of Lake Michigan should be covered in ice.  

With warm waters and almost no ice, air temperatures near the lakeshore become warmer than typical. When air temperatures hover at or just above freezing, snow is unable to accumulate easily, lowering totals.  

Snow will accumulate more readily in areas farther from Lake Michigan where air temperatures are able to drop below freezing.  

"It's best to prepare for difficult travel conditions regardless of how much snow falls, especially Friday night as winds pick up and lead to areas of blowing snow including in Chicago,” Borchardt cautioned.