Isaac Brings Flash Flood Risk to NYC, DC, Charlotte

By , Expert Senior Meteorologist
September 4, 2012; 6:47 AM ET
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Tropical humidity and downpours from the all-but-extinct Isaac will push slowly across the East through the middle of the week.

Isaac was officially downgraded from tropical depression status Saturday, Sept. 1, 2012 at 11:00 a.m. EDT while moving over Missouri. However, problems continue at the local level not only from the weak circulation, but most importantly its tropical moisture.

The slow-moving nature of the downpours will pose a risk of flash and urban flooding. Some locations can pick up an inch of rain per hour during the pattern. Small streams and drainage culverts could quickly overflow, where the downpours persist for a few hours.

RELATED: Isaac to Fuel Storms at Democratic Convention in Charlotte

The potential for localized flooding downpours continues over parts of the South, but will reach as far north as New England as the week progresses, perhaps impacting cities from Atlanta and Charlotte to New York City and Boston.

The downpours will be a major inconvenience for travelers and those heading back to work or school.

Major League Baseball games in the area could experience delays.

The National Football League kicks off their official season Wednesday evening at East Rutherford, N.J. There is the potential for drenching thunderstorms in the area through Wednesday. The humidity will remain quite high. The game is slated for 8:30 p.m. EDT.

The old circulation and tropical moisture from Isaac can also produce locally gusty thunderstorms. There is still a slight risk of a few storms becoming strong enough to down trees and power lines at the local level.

In Charlotte, N.C., for the Democratic National Convention this week, there is the potential for localized flash flooding and gusty thunderstorms through Thursday.

Shower and thunderstorm activity is forecast to diminish, but not completely go away by Friday, as another system approaches from the Midwest and some tropical moisture remains behind.

**Flash flooding occurred in Ocean County, N.J. and Montgomery County, Pa. early Monday morning, EDT. Multiple roadways were closed due to high water.**

**Flash flooding occurred in the Fort Deposit area of Alabama Monday morning. Water was surrounding some homes in the area.**

**Heavy rain has produced flash flooding in Selma, Ala., midday Monday. Many streets were under water.**

Driving at full speed through torrential downpours is dangerous. The visibility can be reduced to a few feet and the water buildup between the road and tires can lead to hydroplaning.

People are reminded to not drive through flooded roadways. The force of the water could carry your vehicle downstream or the road beneath the water could have been undermined.

Over the weekend, even though no longer officially classified as a tropical system, Isaac delivered a general 1 to 6 inches of rain over the Ohio Valley states.

Locally severe thunderstorms also occurred in flow of humid air. There were several dozen separate incidents of damaging thunderstorm winds scattered from Virginia to Mississippi during Sunday alone. During Saturday, a few tornadoes were spawned from Illinois to Arkansas.

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