Relentless rain to raise flood risk in eastern US into this weekend

By Alex Sosnowski, AccuWeather senior meteorologist
May 18, 2018, 1:26:40 AM EDT

A flow of tropical moisture will keep areas from the Southeastern states and the mid-Atlantic to the Ohio Valley wet into this weekend.

Rain will spread northward into the eastern Great Lakes and New England during the weekend.

People with outdoor plans and projects will be greatly challenged by the frequency of rain. Meanwhile, enough rain may fall at a fast enough pace to cause urban and small stream flooding.

Static East Flood Threat This Week

While the areal coverage of rain and thunderstorms will be the most extensive during the afternoon and evening hours, downpours and thunder can occur around the clock in this weather pattern.

Recent rainfall has left the ground saturated in parts of the East.

The combination of prior rain and additional rain may lead to flooding along unprotected areas of some of the rivers. Water levels may approach major flood stage along a portion of the Potomac River this weekend.

Into this weekend, a general 1-3 inches of rain is likely with the potential for additional rainfall to approach 6 inches.

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In a large part of northern Virginia, eastern West Virginia, Maryland, Pennsylvania and New Jersey, it would only take about 1 inch of rain in an hour to trigger flash flooding.

A similar condition exists over parts of the southern Appalachians and Piedmont areas.

Storm that originated from the tropics to enhance rainfall

A system that has taken on some tropical characteristics, or a weak subtropical feature, will push northward over the next several days amid the showers and thunderstorms.

This storm will enhance the rainfall and thunderstorms along the way.

On Friday, torrential downpours and locally strong thunderstorms are likely to focus on the mid-Atlantic region south of interstate 80.

Static Friday Flood Threat NE

During Friday night into Saturday, downpours are likely to drench the eastern Great Lakes and part of New England.

Break of dry weather to advance eastward this weekend

In the wake of that storm, a pocket of slightly drier air may be enough to turn off or at least tone down the downpours in part of the East this weekend.

This lull may extend eastward from the lower Mississippi Valley to the southern and central Appalachians and Piedmont areas on Saturday.

Static Saturday NE Rain 3 pm

The rainfall gap may shift eastward toward the mid-Atlantic coast and much of New England on Sunday. However, downpours may reload over the Mississippi Valley and Appalachians by Sunday afternoon.

The overall pattern may produce frequent wet weather during the balance of May and into early June in much of the East.

The same pattern may yield more concerns for tropical development near the eastern part of the Gulf of Mexico.

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