Irma’s flooding rainfall, tornado threat to expand from Florida to Georgia, Tennessee

By Jordan Root, AccuWeather meteorologist
September 12, 2017, 2:28:26 PM EDT

While the threat for widespread flooding from Irma's rainfall is waning (with the exception of resultant river flooding in parts of Florida), heat and humidity will tax recovery efforts in Florida. You will be redirected to our latest coverage.

After blasting the Florida Peninsula over the weekend, Irma will track inland across the southeastern U.S., threatening flooding, damaging winds and severe weather over a large area into Tuesday.

Irma will put many lives at risk well inland from the coast. Residents in northern Florida, Alabama, Georgia, Tennessee and South Carolina should anticipate severe impacts from Irma.

Irma will travel inland across Georgia and Alabama into Tuesday, continuing to weaken in the process.

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Occasional wind gusts between 40 and 60 mph will be felt across eastern Tennessee, northern Alabama and Georgia, including the cities of Atlanta; Knoxville, Tennessee; Chattanooga, Tennessee; Birmingham, Alabama; and Augusta, South Carolina, into Monday evening.

“The tropical-storm-force winds should expand outward, especially on the east side, to over 300 miles on Monday,” AccuWeather Hurricane Expert Dan Kottlowski said.

Wind of this magnitude can down trees and power lines and cause damage to weak structures.

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People could face power outages, some of which may be lengthy. Now is the time to make sure flashlights are in working order and stock up on extra batteries.

Downed trees can also lead to road hazards for motorists. Alternative routes may need to be taken for those who must travel.

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Irma’s winds will cause water to pile up along the northern Florida, Georgia and Carolina coasts through Monday, inundating coastal communities with several feet of water, including Jacksonville, Florida; Savannah, Georgia; and Charleston, South Carolina.

Irma will dissipate to a tropical depression and eventually a tropical rainstorm over Alabama and Tennessee.

While widespread damaging winds will become less of a concern farther inland, the threat for flooding will mount as Irma's rain expands.

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Irma will bring a heavy swath of rain that will trigger urban and river flooding across the Southeast and into the Tennessee Valley through the middle of the week.

A widespread 2 to 4 inches of rain can fall, with locally higher amounts in the southern Appalachians.

Heavy rain will bring an increased risk for flash flooding and mudslides across the southern Appalachians as Irma’s moisture surges into the mountains.

Small streams and rivers could overflow out of their banks and flood neighboring land and homes. Motorists will need to watch out for road washouts.

“What is left of Irma is expected to slow down and perhaps stall for a time in Tennessee and Kentucky,” Kottlowski said.

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This amount of rain will loosen the soil and will make it easier for wind gusts to topple trees in some areas.

In addition to heavy rain, some areas will have to worry about quick tornado spin-ups within Irma’s outer rain bands to the northeast of the storm’s center.

“These short-lived tornadoes will continue to develop across parts of South Carolina and Georgia on Monday," Kottlowski said.

These type of tornadoes are especially dangerous due to their quick formation and dissipation. Residents will need to quickly take shelter should one form in the area. Heed all severe storm and tornado-related warnings.

During the second half of the week, Irma's rain will spread northeastward into the Ohio Valley and mid-Atlantic.

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