Less than 24 hours after descending upon the Plains states, Winter Storm Petra has 117 million people nationwide under some type of winter weather advisory alert, with 20 million in the Southeastern corridor under advisory for flooding or flash flooding.  

The National Weather Service released a report Tuesday detailing the destructive path of Petra's storm system, which was expected to last until Thursday with no signs of letting up. The NWS advisory has now been extended until Friday. 

The storm, which dropped in the Plains states, is currently passing through the Midwest and the Mid-Atlantic regions and will conclude after reaching the Northeast.

According to the report, a low-pressure system stemming from the Gulf of Mexico "is gathering strength," with a trajectory set for the Ohio Valley and Great Lakes, resulting in heavy rainfall in the Deep South and colder air masses to the north.

Petra, which dropped in the Plains states, is currently passing through the Midwest and the Mid-Atlantic regions and will conclude after reaching the Northeast.

Winter weather advisories are still in place for areas between Omaha and the Twin Cities. Other metropolitan areas affected by this sweep include Wichita, Kansas City, St. Louis, Chicago, Indianapolis, Louisville, Cincinnati, Columbus, and Pittsburgh, many of which have been hit with several inches of snow, and up to a possible projected 10 inches.

In the Baltimore-Washington, D.C. area, 4-to-6 inches of snow is expected, with those near the Maryland-Pennsylvania border predicting up to 8 inches of snowfall. 

Mid-Atlantic states like Virginia, West Virginia, western Maryland, and some parts of Pennsylvania are also forecast to be hit with freezing rain as sub-freezing temperatures give way to warmer air.

In the Northeast, the Philadelphia and New York City metropolitan areas are set to anticipate 2-to-3 inches of heavy snow, though more might accumulate later Wednesday.

In the Southeast, many already experienced heavy rainfall over Tuesday night. Those same areas spanning across northern Alabama, Mississippi, and up towards West Virginia, will continue to endure heavy rains. Parts of Alabama already incurred flash flood warnings overnight.

Tennessee is expected to especially be hit hard, with a projected 5-to-7 inches of rain expected around Memphis and Nashville. 

Northern parts of Georgia will also be affected, with Atlanta preparing for 2-to-3 inches of rain, and possibly higher in the state's mountainous regions.