MIAMI >> A tropical storm warning was issued Thursday from coastal North Carolina to Delaware ahead of a potential tropical cyclone that’s approaching the densely populated East Coast.

The National Hurricane Center announced the formation of “Potential Tropical Cyclone Sixteen” on Thursday morning. The storm was located about 340 miles (550 kilometers) southeast of Charleston, South Carolina, and moving north at 7 mph (11 kph), according to a 8 p.m. advisory from the center. The storm had top sustained winds of 35 mph (55 kph).

The hurricane center defines a potential tropical cyclone as a disturbance that poses a threat of tropical storm or hurricane conditions to land within 48 hours. The current system could reach the North Carolina coast around Friday night or early Saturday.

Meteorologist Maria Torres, a public affairs officer with the Miami-based center, said people along the Atlantic coast need to watch the storm’s progress, gather supplies and make preparations over the next 24 to 48 hours for its arrival.

“This will bring some tropical storm force winds and storm surge along with the high winds to the East Coast through the weekend, mainly from the Southeast to the Mid-Atlantic states,” she told The Associated Press.

The tropical storm warning is in effect from Cape Fear, North Carolina, to Fenwick Island, Delaware. It also includes the Chesapeake Bay south of North Beach, Tidal Potomac south of Cobb Island and Albemarle and Pamlico Sounds.

Virginia emergency management officials warned of heavy rain, high winds and flooding in the next few days.

The Virginia Department of Emergency Management said on social media Thursday that officials are coordinating with local weather service offices to watch the system developing off the coast. Officials called on residents to prepare for the storm and impacts on the region throughout the weekend.

North Carolina Emergency Management warned that large swells from distant Hurricane Nigel also would reach the state’s coast on Thursday, boosting the rip current risk. The combination of those swells and the low-pressure system could mean additional ocean overwash, beach erosion and coastal flooding.

The hurricane center said storm surge between 2 and 4 feet (.6 to 1.2 meters) was expected.

A storm surge warning is in effect from Duck, North Carolina, to Chincoteague Virginia, including Chesapeake Bay south of Windmill Point, and for the Neuse River, the Pamlico River, and portions of Pamlico Sound.

A storm surge watch also was issued from Surf City in North Carolina to Duck, North Carolina, along with Chesapeake Bay north of Windmill Point to Smith Point, the Tidal Potomac south of Colonial Beach and Albemarle and the remainder of Pamlico Sound.

Meanwhile, Hurricane Nigel continued to grow in size late Thursday as it headed toward cooler North Atlantic waters as a Category 1 storm. The hurricane center said Nigel was expected to become a strong post-tropical cyclone in the coming nighttime hours.

Nigel’s maximum sustained winds were 80 mph (130 kph). The system was centered about 630 miles (1020 kilometers) east-southeast of Cape Race, Newfoundland, and moving east-northeast at 37 mph (59 kph). There are no coastal watches or warnings associated with Nigel.