The National Hurricane Center says a tropical depression has formed off the mid-Atlantic coast, but it's not expected to threaten land.

The National Weather Service counts the depression as the first of the 2009 Atlantic hurricane season, which officially begins June 1.

The depression's maximum sustained winds are near 35 mph. Forecasters say it could strengthen to a tropical storm Friday but then is expected to weaken or dissipate by Saturday.

More information on the storm at the National Hurricane Center

Forecasters expect the depression to stay over the Atlantic, where it's moving toward the east-northeast near 16 mph.

Around 11 p.m. EDT Thursday, the depression was centered about 255 miles south-southeast of Nantucket, Mass., and about 500 miles south-southwest of Halifax, Nova Scotia.