Heavy rains hitting the East Coast on Thursday could cause massive flash flooding, damaging wind gusts and a tornado or two.
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More than 25 million people are on flood watch along Interstate 95 in the Northeast. The watch stretches from the New York City area south through much of New Jersey and into northern Delaware, including Philadelphia.
Evening commuters in these areas could experience severe disruption from the storm, which is expected to develop in the late afternoon and continue into the evening.
The storm is driven by a cold front that has already caused flash flooding in central Ohio early Thursday morning. CNN affiliate WBNS reported multiple water rescues and road closures near Columbus, Ohio.
The northeast storm will not last long, but will produce very heavy rain at rates of 1 to 3 inches per hour in some cases.
These torrential rains are notorious for causing flash flooding, especially in urban areas in the east. New York City’s aging sewer infrastructure can only handle about 1.75 inches of rain per hour, which can overflow and cause flash flooding.
As temperatures rise due to pollution from global warming, extreme precipitation is becoming more common because warmer air holds more moisture. Weather systems can act like watery sponges and wring out the moisture, causing locally intense downpours.
Most places will see at least 1 to 2 inches of rain, but areas hit by multiple storms and the heaviest rainfall could see up to 3 to 5 inches in just a few hours.
Some storms could intensify enough to bring damaging winds and hail to many of the same areas at risk of flooding.
Damaging wind gusts will be the most widespread threat, especially in south-central New Jersey, Philadelphia, Delaware and eastern Maryland. The heaviest wind gusts can bring down trees and knock out power.
Isolated tornadoes are also possible north of the severe danger area seen in the image below.
Much of the threat of heavy rain and severe storms should end around midnight as a cold front pushes off the East Coast.
