Stalled Front to Deliver Heavy Rains to Much of Eastern US

Posted: September 22, 2021 1:20 pm

Front Will Bring Persistent Rain and Chance of Severe Weather

A cold front that has been advancing from west to east over the last several days is set to bring heavy rain and cooler temperatures to the eastern half of the US on Wednesday through Friday.

Mild and Dry Conditions Set to Come to an End

While it had been a mild week or two for much of the Eastern Seaboard, that is all about to change with the arrival of this potent cold front. Along with the front will come periods of consistent rain and the threat of severe weather and flash flooding over the next few days. Because this front is moving so slowly, it brings a higher chance of heavy rainfall that can sock a region in with precipitation. This will increase the risk of flooding beginning on Wednesday and continuing through Thursday.

Competing Atmospheric Conditions to Blame

An area of low pressure is setting up surrounding the front, causing it to stall out. A competing area of high pressure positioned off of the East Coast is creating a block that the showers will not be able to punch through. These competing areas of pressure will cause the rain to persist in the area, raising the risk of flash flooding. This threat will be particularly high in areas hit hard by Tropical Storm Ida last month.

In addition, tropical moisture moving up from the south will become lodged along the front. This will also increase the potential of severe weather. The heaviest rain is expected in Ohio, Indiana, Michigan, Pennsylvania, West Virginia, and western portions of New York state, Maryland, Virginia.

Firehouse Effect Possible

Much of the central Appalachians is at risk of the firehose effect which happens when rain pounds down at a rate of 1-2 inches per hour for several consecutive hours. The greatest risk of this type of rainfall will happen on Wednesday night. Rainfall in these amounts may cause sudden urban flooding and a significant rise in water levels in small streams and other waterways. Forecasters are asking residents to be aware of this type of danger.

This risk will also exist along the steep terrain of the Allegheny Mountain communities and along the streams and rivers throughout western Pennsylvania, western New York state, and West Virginia.

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Wednesday night could be a time of severe weather for eastern Ohio stretching into western Pennsylvania and down into southern West Virginia. This active weather pattern has the potential of producing thunderstorms, damaging wind gusts, and isolated tornadoes.

Because the front has been moving at a snail’s pace over the last few days, the heaviest rain is not likely to hit the far East Coast until Thursday. Cities such as Philadelphia, and Washington, DC will likely see rain developing on Thursday with the far reaches of Boston and New England not experiencing the worst of the weather until Friday. This rain may hang around in New England until early Saturday before the front finally finishes its trek across the entire US.

Most areas of the mid-Atlantic can expect to see 1-2 inches of rain out of this weather maker. However, up to six inches of rain may be possible for areas farther to the north, including central Pennsylvania and western New York state.

What is Next?

After this front exits the region, a second weather system is forecast to drop into the Great Lakes on Saturday. While this system may deliver spotty rain showers, it will not be anything like what the region is set to see in the coming days. However, this second system will bring along plenty of cool air to remind everyone that fall is officially here.