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.

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 re-strengthening tropical storm, AccuWeather meteorologists say. The heavy rainfall may ruin vacation and outdoor plans as well as cause travel delays and pose a threat to property.

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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 from portions of the central Appalachians and mid-Atlantic to New England. The downpours and thunderstorms will focus on different areas each day.

Into Monday night, the main zone of drenching showers and gusty thunderstorms will extend from southern Michigan into northern Ohio and Maine.

The showers and thunderstorms will be due to the leading edge of a southward-sagging batch of cooler, less humid air from Ontario and western Quebec.

A separate zone of severe weather, one that could lead to a few tornadoes will exist over part of the Upper Midwest into Monday night.

On Tuesday, the leading edge of this cool push will dip farther south and set off more drenching showers and gusty thunderstorms with some risk of severe weather from strong wind gusts from Ohio through much of Pennsylvania, Maryland, Delaware and New Jersey. The northern parts of West Virginia and Virginia are in the severe weather risk zone, along with part of the New York City metro area. The AccuWeather Local StormMax™ wind gust is 70 mph, which is just under hurricane strength.

The zone from near the border of Pennsylvania and Maryland to Delaware and southern New Jersey may be at a moderate risk of severe weather which includes the metro areas of Philadelphia and Baltimore.

"Tropical air from the periphery of Debby's influence will push up into the frontal zone from Tuesday to 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, where rain falls local amounts could approach 4 inches.

"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.

"Next, Debby's impacts will have to be dealt with probably ramping up quickly on Friday," Dombek warned.

Debby 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.

The exact track and intensity of Debby will influence the extent and magnitude of the tropical downpours that spread northward from Friday to Saturday.

A Debby track that hugs the mid-Atlantic coast will be more likely to throw heavy rain farther inland into the mid-Atlantic and New England, perhaps back to the Appalachians, Dombek explained. A Debby track that is more to the east and southeast may cause heavy rain to fall only along the immediate mid-Atlantic and southeastern New England coasts.

"Where the heavy rain from the midweek storms and Debby overlap, there is the potential for 6-8 inches and locally higher amounts," Dombek said.

Rainfall of this magnitude would be enough to trigger small stream flooding and rises 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.

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," AccuWeather Chief On-Air Meteorologist Bernie Rayno.

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

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