Tropical Storm Debby to turn northward, drench northeastern US

Debby is forecast to turn northward and drag bands of heavy rain into the Northeast. Some areas will be drenched with drought-easing showers and others drowned by torrential downpours that can trigger flooding.

After gaining its second wind and grabbing more moisture from the Atlantic, Debby will swing up and across the interior northeastern United States late this week with rain heavy enough to trigger flooding in some areas, as well as gusty winds and even severe thunderstorms capable of producing tornadoes near the coast, AccuWeather meteorologists warn.

Debby is forecast to track inland over North Carolina on Thursday then take a curved path along the Appalachians through the Northeast from Friday to Saturday. As this inland track occurs, Debby will transition from a tropical storm to what AccuWeather meteorologists refer to as a tropical rainstorm.

Debby's greatest threat: Flooding rain

Only Debby's increasing speed will be somewhat of a limiting factor for rainfall, which will still range between 4 and 8 inches from much of Virginia and eastern West Virginia through western and central Maryland, a large part of Pennsylvania, central and eastern upstate New York, western New England and part of southern Quebec. Within this zone, there is an AccuWeather Local StormMax™ of 1 foot of rain.

Much of the interior Northeast will be at high risk to lives and property from Debby, largely due to the impacts of heavy rain and the likelihood of flooding.

"In many areas of the Northeast, much of the rain will not be absorbed by the landscape very well and quickly run off into basements, catch basins, small streams and then the larger rivers," AccuWeather Senior Director of Forecast Operations Dan DePodwin said.

It is possible that flash flooding will evolve into a life-threatening situation in some communities over the interior Northeast.

Flooding in urban areas and along small streams is a certainty. Motorists should be prepared for flooded roads or portions of roads that may have been washed out or filled with gravel and other debris in hilly areas.

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Summer-long drought conditions, for example, in parts of western Virginia and West Virginia may negate some of the rain's effects. However, even in drought locations, enough rain may occur to lead to at least some incidents of urban flooding and rapid rises on small streams.

Some areas that have been repeatedly hit by flooding this summer, such as parts of Vermont and New Hampshire, could be hit hard again by downpours by the end of the week.

Biggest rain from Debby may miss DC, Philly and NYC, but flooding still possible

"Even along portions of Interstate 95 and the immediate Atlantic coast in the Northeast, torrential downpours in days prior to Debby's arrival have saturated the ground, so it may not take as much rain to lead to flash flooding and rises on the rivers," AccuWeather Meteorologist Joseph Bauer said.

Part of the New York City area received 1-3 inches of rain from downpours on Tuesday. From 3 to 6 inches of rain swamped the Trenton, New Jersey, area, and some of the eastern and western suburbs of Philadelphia were also swamped with downpours.

"Some of the same sort of troublesome pre-Debby downpours will occur Wednesday to Thursday from parts of the central Appalachians to the mid-Atlantic," Bauer explained, "A southward-sagging front is likely to be the main trigger into Wednesday night, then that front will reverse direction on Thursday as tropical air ahead of Debby pushes northward."

Even though much of the I-95 zone may miss the heaviest total rainfall from Debby, enough rain will occur to lead to incidents of flash urban flooding that can lead to major travel disruptions, especially from Friday to Friday night in the mid-Atlantic and western New England and later Friday to Saturday in eastern New England.

Strong winds, coastal flooding and tornadoes a threat in coastal Northeast

With Debby to track inland, winds and tropical air will kick up on the storm's eastern flank and cause trouble along the mid-Atlantic and New England coasts.

Strong south-southeast winds will expand over the mid-Atlantic and much of New England as Debby moves northward. Gusts during and outside of thunderstorms will frequent 40-60 mph with an AccuWeather Local StormMax™ gust of 70 mph, which is most likely on the higher peaks in the Presidential Range in northern New England and along the New England coast.

"The combination of tropical-storm-force winds will have trees bobbing and tipping in the saturated soil, and a number may topple over that can lead to property damage and power outages," AccuWeather Meteorologist Brandon Buckingham said.

The winds will push Atlantic Ocean water into area bays and tidal rivers, leading to flooding, which will be greatest at times of high tide.

A storm surge of 1-3 feet is forecast with locally higher levels on portions of the Chesapeake, Delaware and Narragansett bays, as well as Baltimore and New York harbors and the tidal portions of the Potomac, Delaware, Hudson and Connecticut rivers.

Even though Debby is likely to transition to more of a non-tropical system, it will retain enough tropical characteristics and bands of thunderstorms, especially near and east of the storm center for a time.

Because of this brief tornadoes may be spawned.

Some of the tornadoes could be wrapped in rain and difficult to see approaching. Where these occur along the coast, waterspouts are also possible.

Debby to draw in cooler, less humid air in its wake

Debby will become intertwined with a non-tropical storm approaching from the Upper Midwest late this week.

The pair of systems will then speed off to the northeast and into southern Canada this weekend. West to northwest breezes in the wake of the storm duo will then draw in much cooler and less humid air across the Northeast. It may take until Saturday night or Sunday for that less humid air to reach the Atlantic coast.

The weather will improve from northwest to southeast across the region this weekend. However, some may be nervously watching river levels.

It often takes several days after a heavy rain event for the larger rivers to fully respond to the runoff. Because of the amount of rain that is forecast to fall from Debby and prior downpours, some rivers in the region may experience moderate to major flooding this weekend to early next week.

Those living along or have commercial or agricultural property along flood-prone rivers without levee protection may need to take preventative action.

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