Rain from Debby to follow midweek downpours, severe weather in Northeast

Following troublesome rounds of rain and severe weather into midweek, downpours from Tropical Storm Debby may add to travel and flooding issues in part of the Northeast to end this week. Major flooding is likely.

Rounds of problematic heavy rain will continue to hit portions of the northeastern United States into the weekend. First, from thunderstorms in the Midwest, then from the tropics as Debby is likely to make a run at coastal areas as a tropical rainstorm or possibly a restrengthening tropical storm, AccuWeather meteorologists say. The heavy rainfall may not only slow travel and ruin vacation and outdoor plans, but a risk to lives and property will arise due to flooding.

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Before Debby arrives late this week, there will be episodes of flooding downpours and severe thunderstorms packing strong wind gusts into Wednesday night from portions of the central Appalachians and mid-Atlantic to New England.

Into Tuesday night, the leading edge of this cool push dipped farther south and set off more drenching showers and gusty thunderstorms with some reports of severe weather from strong wind gusts from Ohio through much of Pennsylvania and New Jersey.

"Tropical air from the periphery of Debby's influence will push up into the frontal zone through Wednesday, adding water to the air that will, in turn, be squeezed out," AccuWeather Senior Meteorologist Dave Dombek explained. "This will enhance the downpours and correspondingly raise rainfall amounts to a higher level than if there had been no tropical moisture in the first place."

Widespread rainfall of 1-2 inches is likely through midweek, and local amounts could approach 4 inches Much of that rain may fall in an hour's time. Where the heaviest rain falls, quick urban and small stream flooding will occur.

"Somewhat of a lull in shower and thunderstorm activity is likely from Wednesday night to Thursday," Dombek said.

There will still be some drenching showers and thunderstorms from the central Appalachians to the mid-Atlantic Thursday. Levels on some streams may be elevated.

"Next, Debby's impacts will have to be dealt with, and problems will ramp up quickly on Friday as rain spreads northward," Dombek warned.

Debby's impacts on northeastern US

After dumping feet of rain while crawling through coastal areas of the southeastern U.S. into Thursday, Debby is forecast to pick up speed later this week. Debby may degrade to a tropical rainstorm while over the Carolinas, especially if the center ventures well inland of the coast as forecast.

The exact track and intensity of Debby will influence the extent and magnitude of the tropical downpours that spread northward from Friday to Saturday. Increasing forward speed will limit the amount of rain, but rainfall is still likely to be heavy to excessive.

With a track just inland of the coast as Debby churns through the mid-Atlantic, the corridor of heaviest rain will be inland of the coast -- just north and west of the storm center.

From Debby alone, a strip where 4 to 8 inches of rain will fall will extend northward from central and eastern Virginia to central and eastern Maryland, much of Delaware, eastern Pennsylvania, part of northern New Jersey, eastern upstate New York and a portion of central New England. Within this zone, there is an AccuWeather Local StormMax™ of 1 foot of rain. It is important to note that this anticipated rainfall from Debby is on top of what falls through Wednesday afternoon, associated with a non-tropical storm and cool front.

In less than five days, from two to three months' worth of rain may fall on parts of the mid-Atlantic, the central Appalachians and New England from the combined effects of the non-tropical storm, cool front and Debby into Saturday.

Rainfall of this magnitude would be enough to trigger rapid small stream flooding, moderate to major flooding on some of the rivers regardless of prior drought. Those living along unprotected areas of the coastal rivers should closely monitor the situation late this week and be prepared to take action to save property and move to higher ground if necessary.

Current National Weather Service river level forecasts may not be capturing all of the rainfall potential this early week and may not reveal the true crests of area streams and rivers late this week and beyond. It may take up to a few days after the rain from Debby comes and goes for some of the larger rivers to crest. This is why AccuWeather meteorologists refer to river flooding as a slow-moving disaster.

While wind from Debby is not likely to be a major concern for much of the Northeast, it will temporarily create stormy conditions along the mid-Atlantic coast.

"There is some potential for Debby to strengthen enough to bring moderate to strong tropical storm conditions to southeastern New England, depending on the track from Friday night to Saturday," said AccuWeather Chief On-Air Meteorologist Bernie Rayno.

There may be some time for restrengthening if the center of Debby is able to track along just south of the New England coast, while a track inland from the coast would prevent that.

Regardless, there will likely be a period of above-normal tides, rough surf, beach erosion, and even coastal flooding in part of the mid-Atlantic Friday and in southeastern New England from Friday to Saturday.

For example, a storm that tracks northward into central Virginia and southeastern Pennsylvania will result in south-to-southeast winds that push water up into the Chesapeake and Delaware bays. Surging water levels can lead to coastal flooding in cities such as Baltimore and Philadelphia.

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