A powerful storm system set to affect much of the country this weekend could pose a triple threat, with the possibility of severe storms and tornadoes, ice and snow, and flooding.
Millions of people in the eastern half of the United States -- in the Southeast, Midwest, Great Lakes Region and the Northeast -- could feel the effects, said CNN meteorologist Dave Hennen. Another storm system will bring heavy snow to the West.
In the eastern US:
- Nearly 50 million people are under flood watch in parts of Texas, Oklahoma, Arkansas, Missouri, Kentucky, Illinois, Indiana, Ohio, New York and Vermont.
- About 35 million are under a winter weather alert in parts of Oklahoma, Kansas, Nebraska, Iowa, Illinois, Wisconsin, Michigan, New York, New Hampshire, Vermont and Maine.
- And more than 20 million are under a wind advisory in parts of Texas, Louisiana, Alabama, Mississippi, Florida, Kentucky and Indiana.
Here's how the regions could be affected.
Tornadoes and damaging winds across the South
Severe weather, possibly including tornadoes, damaging wind and large hail, is predicted in much of the South on Friday and Saturday, Hennen said.
The risk of damaging wind gusts became even more apparent Thursday, prompting the National Weather Service's Storm Prediction Center to issue a moderate risk of severe weather -- at level 4 of 5 -- for areas between Tyler, Texas, and Memphis, Tennessee, including Little Rock, Arkansas, and Shreveport, Louisiana.
Residents from the Gulf Coast north to Missouri could be hit by severe weather Friday afternoon and into the overnight hours. The greatest threat encompasses cities in eastern Texas, like Dallas and Houston, as well as Shreveport, Louisiana, Hennen said.
"Storms will go well after dark, with tornadoes after dark," Hennen said. "Tornadoes at night are more than twice as deadly as those that occur during the day, with people not getting the warnings in time."
On Saturday, the danger will shift to cover much of the Southeast, including cities like New Orleans and Baton Rouge in Louisiana; Birmingham, Montgomery and Mobile in Alabama; and Atlanta.
Residents in these regions should "make sure your smartphone weather notifications are turned on. Some of these storms will be traveling at 60 mph, and you may only have minutes to react," said CNN meteorologist Chad Myers.
Snow and ice in the Midwest
Colder areas to the north could feel the effects of a significant snow and ice storm, which the National Weather Service in Chicago called a "powerhouse storm system."
Parts of Illinois, southern Wisconsin and Michigan could see heavy snow fall as the storm moves east, with 6 inches of snow possible in some areas, Hennen said. Upstate New York and New England could see snow as well.
A dangerous ice storm will form over the Great Lakes region. Between 6 and 12 inches of snow is expected in northern Michigan, Hennen said, and ice accumulation there could down trees and power lines.
"We certainly have a complicated mess on our hands," the National Weather Service in Grand Rapids, Michigan, said.
A flooding threat from Texas to Michigan
Millions of people from Texas to New England were under a flood or flash flood watch Friday morning.
Cities put on notice included: Tulsa, Oklahoma; Little Rock; Memphis; St. Louis; Indianapolis; Chicago; Detroit; and Buffalo, New York.
Widespread rainfall totals between 3 and 5 inches were expected, Hennen said, with higher amounts possible in local areas.
Heavy snow in the Northwest
A separate round of storms will bring heavy snow into the higher elevations of the Northwest, Hennen said.
Winter storm watches were posted for the Cascades and the northern Rocky Mountains, with the weather service predicting snowfall of up to 2 feet. The threat there includes avalanche danger, with warnings posted in parts of Idaho and Montana.
CNN meteorologist Robert Shackelford contributed to this report.