Eastern US to face renewed risk of flooding, disruptive downpours this week

By Kristina Pydynowski, AccuWeather senior meteorologist

July 30, 2018, 11:00:17 PM EDT

Following the break of dry weather in the mid-Atlantic this past weekend, downpours have already begun to overspread the eastern United States early this week.

Tropical moisture will once again surge northward between a slow-moving storm and a strong area of high pressure offshore (called the Bermuda High) into early August.

That will lead to sticky conditions and rounds of drenching showers and thunderstorms streaming from the South to the central Appalachians and the mid-Atlantic through most of the week.

"Rainfall last week was concentrated along the mid-Atlantic coast to the central Appalachians," according to AccuWeather Senior Meteorologist Alex Sosnowski.

"This week, rainfall may be spread over a broad area from the northeastern Gulf and southern Atlantic coasts to part of the Ohio Valley, mid-Atlantic coast and eastern Great Lakes," Sosnowski said.

Residents from Baltimore to Harrisburg and Williamsport, Pennsylvania, should not let their guard down, as there is the potential for heavy enough rain to renew flooding problems.

"Locally heavy rain can easily trigger new issues due to the large amount of rain this part of the country has received recently," AccuWeather Meteorologist Rob Richards said.

Downpours can quickly flood low-lying and urban areas, as well as bring swollen streams and smaller rivers out of their banks.

In addition to the risk of flooding, some of the storms can produce isolated damaging wind gusts. Any locally gusty storm may easily topple trees in the saturated soil.

Flooding issues and locally severe thunderstorms may not just be confined to areas that were hit hard last week.

One area that can face some of the highest rain totals of the week and the greatest concern for flooding may be the southwestern- or southern-facing slopes of the Appalachians from northern Georgia to West Virginia. Mudslides can also be triggered.

A general 3-6 inches of rain is forecast in these areas with locally higher amounts through the course of the week.

"Anywhere storms gather and linger for a few hours, daily rainfall could approach 3 inches and rainfall for the entire week can top 6 inches," Sosnowski said.

Even where flooding does not ensue, the frequent showers and thunderstorms will plague sports teams, farmers, construction crews and anyone else with outdoor plans. Remember that as soon as thunder is heard, the risk for being struck by lightning is present.

Flooding can lead to road closures, while downpours can reduce visibility and heighten the risk of vehicles hydroplaning when traveling at highway speeds. Airline passengers should prepare for potential delays.

Download the free AccuWeather app to stay alert for severe weather and to receive information on upcoming rainfall and flooding dangers.

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Downpours are expected to expand over the Ohio and Tennessee valleys and into the eastern Great Lakes early this week. This rain can spread to the St. Lawrence Valley by midweek.

The most persistent of these downpours can lead to areas of flash flooding.

"On the other hand, the same mechanism that kept rainfall to a minimum along the upper mid-Atlantic coast and in much of New England last week may come into play once again this week," Sosnowski said.

The Bermuda High may bulge far enough to the west to shorten the duration of shower and thunderstorm activity along the coast from near New York City to Boston and Portland, Maine.

Even on the days when stormy weather is absent, beachgoers throughout the Eastern Seaboard should use caution. Gusty winds will stir choppy seas and bring an increased risk for rip currents. 

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