(CNN)A tornado touched down in the Atlanta area on Monday morning as severe weather threatened more than 100 million people from the southern Plains through the Mid-Atlantic.
A tornado warning was issued at about 10:30 a.m. and lasted until 11:15 a.m. ET, with about 450,000 people in its potential path, according to the National Weather Service in Atlanta.
The extent of the storm’s damage wasn’t clear early Monday afternoon. Mayor Keisha Lance Bottoms tweeted photos of downed trees in her neighborhood in southwest Atlanta, while Dru Ghegan, the owner of Bonded Service Warehouse in Fulton County, shared photos that show the building suffered significant damage.
The storm that prompted the warning was moving to the eastern metro area and has weakened. A severe thunderstorm warning was in effect until 12 p.m. for parts of central DeKalb and southwestern Gwinnett counties, including Lawrenceville, Lilburn and Stone Mountain.
Overall, a tornado watch is in effect until 4 p.m. ET for parts of Georgia and Alabama, including Atlanta, Macon and Montgomery, as additional thunderstorms could produce a few tornadoes in this watch area through the afternoon. Hail up of to 1 inch and damaging winds up to 70 mph are possible with some of these storms.
The alerts came a day after tornadoes struck at least three cities in Mississippi, causing damage to buildings and knocking out power. The same system that spawned tornadoes over the weekend is still on the move, bringing the threat for the severe storms across the Southeast.
In addition, over the Plains, a new system is developing and will spark a separate outbreak of severe weather into the overnight hours.
Tornadoes most likely in southern Plains and Ohio River Valley
The greatest risk for severe weather through Monday night will be from Texas through Kentucky, where there is a level 3 out of 5, enhanced risk, according to the Storm Prediction Center. This includes Dallas, Fort Worth and Arlington in Texas, Fort Smith and Fayetteville in Arkansas, and Paducah in Kentucky.
This region has the best chance of seeing damaging winds, but large hail and tornadoes are also possible, especially in southeastern Oklahoma and northeastern Texas.
“Very large hail, tornadoes (a couple of which may be significant), and intense damaging winds are expected,” according to the Storm Prediction Center.
Showers and storms Monday morning were to exit the Ohio River Valley by midday, while the southern Plains remain dry most of the day.
By late afternoon, quickly moving thunderstorms will begin to form and they will persist into the night. Some of these storms are forecast to be supercells, which spin and can produce tornadoes. This tornado threat will continue into Monday night.
“A tornado risk may persist into the overnight hours as storms move from Oklahoma into parts of Arkansas/southern Missouri and approach the Mississippi River late,” according to the SPC.
Rounds of storms are possible overnight, so some locations could get hit by more than one storm — perhaps more than one severe storm.
These storms may not reach the western Ohio River Valley until early Tuesday, possibly impacting cities including Nashville, Indianapolis, St. Louis and Louisville.
Severe storms also threaten in Southeast
Monday’s severe weather threat extends across the Southeast. A level 2 out of 5, slight risk is in place for Atlanta, Birmingham, Charlotte, Charleston, Raleigh and Virginia Beach.
Marginal, level 1 out of 5, chances for severe storms stretch from the deep South through the Mid-Atlantic. Cities including Washington, Richmond and Savannah are all included in this risk area.
Unlike in the central US, the threat in the Southeast will primarily be during the daylight hours.
There have already been thunderstorms this morning, and additional storms will form during the latter half of the day.
This round will need to be watched for severe storms this afternoon and evening. Reports of tornadoes, hail and damaging winds are expected with some of the storms. Localized flash flooding will be possible with any of today’s storms, with some locations measuring 1 to 3 inches of rain.
Many states across the Southeast have seen double their normal rainfall over the last month, so even 1 to 2 inches of additional rain could lead to flash flooding.
Storms trek east Tuesday
The threat doesn’t end on Monday, however. The storm system over the Plains will make its trek toward the East Coast, fueling the risk for severe weather from the Gulf Coast through the eastern Great Lakes on Tuesday.
This puts Mississippi back at risk for tornadoes, but tornadoes could especially be possible in parts of Louisiana, Alabama and Tennessee as well, where there is a level 3 out of 5 severe weather risk.
“Large hail, damaging wind gusts and a few tornadoes will be likely along with rainfall rates in excess of an inch per hour,” said the National Weather Service office in Jackson, Mississippi.
A few showers and storms could be possible during the day, especially in the Tennessee River Valley, but the main event will be Tuesday evening into Tuesday night across the Gulf Coast states.
A squall line is expected to form, making for widespread storms. This line is expected to reach as far north as the Great Lakes, but the storms will likely be more scattered.
Flash flooding will be possible across the South thanks to the combination of heavy rainfall and all the rain that has fallen in recent days and weeks. A widespread 1-3 inches of rain is forecast across this region into Tuesday night.
This line of storms should weaken by Wednesday morning as it approaches the East Coast of the US, but isolated severe weather will remain possible.
CNN’s Monica Garrett and Eric Levenson contributed to this report