Tropical Storm Debby to push inland, threaten Appalachian flooding

As Debby presses inland and swings over the northeastern United States, torrential rain will ease drought in some areas but bring flash flooding of urbn areas and small streams as well as major river flooding.

After gathering more moisture from the Atlantic earlier this week, Debby will swing up and across the interior northeastern United States to unload rain heavy enough to trigger flooding in some areas and raise the possibility of a few tornadoes, AccuWeather meteorologists warn.

Debby will continue to track inland over the Carolinas on Thursday before swinging across Virginia, Maryland, Pennsylvania and upstate New York from Thursday night to Friday night. During this time, Debby will transition from a tropical storm to what AccuWeather meteorologists call a tropical rainstorm. This designation intends to continue to raise public awareness of ongoing impacts that may be damaging and life-threatening.

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 quickly into a life-threatening situation in some communities of 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.

• Have the app? Unlock AccuWeather Alerts™ with Premium+

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 fall 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.

Farther to the east, in the Interstate 95 corridor from Washington, D.C., to Philadelphia, New York City and Boston, the main threats from Debby will be associated with flash urban flooding, storm surge flooding, strong wind gusts and even tornadoes.

Strong winds, tornadoes a threat in part of interior Northeast

With Debby to track inland, winds and tropical air will kick up on the storm's eastern flank and cause trouble.

Strong south-southeast winds will expand as Debby moves northward. Gusts during and outside of thunderstorms will range from 40-60 mph from parts of the Appalachians to the Atlantic coast with an AccuWeather Local StormMax™ gust of 70 mph. The StormMax 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.

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, making iy difficult to see them 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 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.

River flooding to continue in Debby's wake

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 earlier downpours, some rivers in the region may experience moderate to major flooding this weekend into early next week.

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

Want next-level safety, ad-free? Unlock advanced, hyperlocal severe weather alerts when you subscribe to Premium+ on the AccuWeather app. AccuWeather Alerts™ are prompted by our expert meteorologists who monitor and analyze dangerous weather risks 24/7 to keep you and your family safer.