Debby downgraded to tropical depression; floods threaten Carolinas, western Va.

Aug. 6 (UPI) -- Tropical Storm Debby was downgraded to a tropical depression on Thursday but was still potent enough to keep major flooding warnings in place in parts of the Carolinas and western Virginia.

Fifteen hours after making its second landfall in the United States near Bulls Bay, S.C., early on Thursday morning, Debby was officially downgraded but was still packing plenty of rainfall.

As of 5 p.m. EDT, the center of now-Tropical Depression Debby was located about 45 miles east of Charlotte, N.C., moving north-northwest at 10 mph, with maximum sustained winds of 35 mph, the National Hurricane Center said in an update ,

With Debby likely weakening into a post-tropical cyclone by Friday, the main threat remained exceedingly heavy rain over parts of the mid-Atlantic south.

An additional 3 to 6 inches of rainfall with locally higher amounts was forecast along with "considerable flooding" across parts of eastern South Carolina and southeast North Carolina through Friday.

The worst-hit parts of South Carolina were in line for a catastrophic maximum storm total of 20 to 25 inches following an additional 1 to 3 inches on Thursday, while parts of southeast North Carolina were expected see another 3 to 6 inches, pushing totals there to as high as 15 inches.

"Locally catastrophic flash and urban flooding" were also forecast for a broad swath of the Atlantic seaboard stretching northward from central North Carolina across portions of Virginia. Those areas could expect 3 to 7 inches with local amounts to 10 inches, forecaster said.

In Charlotte, officials and residents prepared for flash flooding as Duke Energy reported more than 24,000 customers in Mecklenburg County were without power as of Thursday morning.

Dozens of downed trees were reported across the city of Charlotte as a flash flood warning remained in place until 7 p.m.

The remnants of Debby were also expected to dump 2 to 4 inches of rain on parts of Maryland north through upstate New York and Vermont.

The storm first made landfall in Florida's Big Bend area Monday as a Category 1 hurricane, before weakening as it moved across the eastern coasts of Georgia and South Carolina. It made its second landfall around 2 a.m. Thursday about 20 miles northeast of Charleston, S.C., and 65 miles southwest of Myrtle Beach, S.C.

Debby may produce "a few tornadoes" starting Thursday night in an area stretching from central and eastern North Carolina into central and southeast Virginia, with the threat shifting northward into parts of New Jersey and eastern Pennsylvania on Friday, the NHC said.

Meanwhile, potentially life threatening surf will continue to affect the southeastern U.S. coast for "another day or so," officials said.