Hurricane Erin is marching north, lashing North Carolina's Outer Banks with rough waves and coastal flooding, and bringing a threat of dangerous waves and potentially deadly rip currents to the East Coast. Due to the high surf and rip current risk, New York City is extending its swimming ban.

The Outer Banks — essentially sand dunes sticking out of the ocean a few feet above sea level — are vulnerable to erosion. Storm surges can cut through them, washing tons of sand and debris onto roads and sometimes breaking up pavement and creating new inlets.

Although the storm is expected to stay offshore, it will produce dangerous surf conditions for much of the Atlantic Coast this week, forecasters say.

Increased surf and dangerous rip currents are expected to continue along the eastern seaboard as Hurricane Erin moves into the North Atlantic.

Hurricane Erin on Wednesday grew in size as it made its way up into the Atlantic off the U.S. East Coast with tropical-storm conditions forecast to hit North Carolina and dangerous surf left