02:04 - Source: CNN
March ends like a lion for the eastern US
CNN  — 

Millions of people across the Southeast are under the threat of severe weather, including heavy rain and possibly isolated tornadoes, through Wednesday night.

Heavy rain that could cause flash flooding is forecast to impact the Tennessee Valley through Kentucky. This includes the metro area of Nashville, which was hit hard by flooding over the weekend.

Over 39 million people from Louisiana through the Mid-Atlantic could see severe storms. The largest impacts from these will be damaging straight line winds from the Gulf Coast through the Carolinas; however the potential for isolated tornadoes exists with these storms as well.

After this extreme weather passes, the temperatures will plummet to sub-freezing in the overnight hours with the potential for snow across the Appalachians into New England.

A utility building was carried down a flooded creek in Nashville Sunday.

Communities still recovering

The newest severe weather forecast follows a storm that left at least seven people dead and caused widespread damage around the Nashville area last weekend.

The heavy rain prompted flash floods that swept cars into inescapable currents, and damaged dozens of homes and buildings.

Further south, cities in Alabama and Georgia are still cleaning up from terrifying tornadoes that tore through, killing six people, last week.

A tornado damaged a home in Historic Newnan, Georgia, on March 26, 2021.

The tornadoes damaged dozens of homes and businesses across the two states.

In Alabama, the community of Eagle Point saw roofs ripped off houses, trees plucked from the ground, and power lines downed across roadways.

In Georgia’s Coweta County, the city of Newnan was hit by a powerful EF-4 overnight, with residents being warned by sirens 15 to 20 minutes before the tornado hit, residents told CNN.

The storms killed at least one person in the county, Fire Chief Deron Patrick Wilson said.

“This stuff is unbelievable. I kind of think about this kind of stuff when you look out in the Midwest, Oklahoma. I think you’re going to see that same kind of damage here,” Wilson said.

Warm and cold air masses causing chaos

Meantime, parts of the country are experiencing sharp fluctuations in conditions within a short period of time.

A cold Canadian air mass to the west has bumped against warm air as it moves east, creating winds in excess of hurricane strength in areas.

Wind gusts of 79 mph were reported in Hettinger County, North Dakota, just to the south of Dickinson, on Monday, a part of the same front and winds that caused the fires in South Dakota.

A record high of 81 degree Fahrenheit was recorded in Aberdeen, South Dakota, on Monday – 33 degrees above normal. After winds pushed the cold mass in, temps struggled to reach 39 degrees.

Below average temperatures are surging into the eastern United States on Wednesday behind a cold front, with the exception of one last warm day across eastern New England.

As that cold front passes – temperatures will also drop dramatically, putting more than 21 million under freeze watches or warnings from the Central Mississippi Valley through the Ohio Valley through the mornings of Thursday and Friday, where temperatures will be in the upper 20s.

Freeze watches and warnings and frost advisories are in effect for the cold air expected Thursday and Friday mornings

It will even be cold enough for lake-effect snow for portions of the Great Lakes: “The core of the cold air (in the atmosphere) will spread over Lake Michigan tonight into early Thursday, which brings us into the month of April. Not too often we discuss lake effect snow in April, but this will be one of those/albeit brief periods,” said the National Weather Service office in Chicago.

Winter weather will also be seen again across the Appalachians of West Virginia, the Eastern Great Lakes into portions of New England between Wednesday night and Thursday night. Six to 10 inches of snowfall is expected western and Upstate New York, with lower totals elsewhere.

Meanwhile across the western US, temperatures are above average midweek, but by later this week that milder air will shift east into the central US.

Widespread high temperatures of 5-15 degrees above average are forecast by Friday from the West through the Great Lakes. The northern Plains will be the warmest relative to normal, with temperatures up to 30 degrees above average.

Forecast high temperatures on Sunday

Temperatures will warm up further for the Easter weekend, with potentially record-breaking highs up to 40 degrees above average for the northern Plains. By the end of this weekend, coast-to-coast warmth is forecast except for portions of the Northwest and Florida.

CNN’s Jackson Dill contributed to this report