MIAMI -- Subtropical Storm Gustav formed Sunday in the Atlantic off North Carolina, with its outer bands of wind and rain expected to reach the coast Monday, forecasters said.

A tropical storm watch was ordered from Cape Fear, N.C., to the Virginia border. Forecasters at the National Hurricane Center in Miami expected the storm to strengthen by midweek.

"Before the system gets even closer, they will start feeling the winds pick up to tropical storm force," said meteorologist Jorge Aguirre.

At 8 p.m., Gustav was about 385 miles southeast of Cape Hatteras, N.C., with sustained winds of 40 mph, forecasters said.

The storm was moving toward the west-northwest at nearly 15 mph. Gustav was expected to slow somewhat and move gradually to the northwest.

Computer forecasts had Gustav's center nearing the U.S. coastline by Tuesday morning.