Hurricane Alert Stretches 500 Miles Along East Coast : Weather: Residents are warned from Carolinas to Chesapeake Bay. Frontal systems make it hard for forecasters to predict the storm’s path.

A hurricane watch was posted Sunday along about 500 miles of the Eastern Seaboard as Hurricane Emily spun slowly but steadily toward what could be a punishing collision with one of the most vulnerable sections of the U.S. coast.

Residents in the area--which runs from just north of Charleston, S.C., to the Delaware-Maryland border and includes Chesapeake Bay--were told that the storm would most likely reach land Tuesday morning.

“This means that those areas have the potential for the storm to come in within 36 hours,” Bob Sheets, director of the National Hurricane Center, said Sunday afternoon. He added that hurricane warnings narrowing the area where Emily would likely reach shore would go up this morning.

“I know a lot of people are getting ready,” said Melissa Mehaffey, front desk clerk at a Wilmington, N.C., motel. “I’m not too worried yet, but maybe ignorance is bliss, huh?”

As of 11 p.m. EDT Sunday, Emily remained a dangerous hurricane, with top winds estimated at 85 m.p.h. Forecasters said the storm was located some 390 miles southeast of Cape Hatteras, N.C., and moving in a northwesterly direction at 9 m.p.h.

But Sheets warned that Emily was likely to gain strength today as it made a path across the warm waters of the Gulf Stream. The forecast still called for Emily to grow, with sustained winds topping 100 m.p.h.

Along with destructive winds, a storm of Emily’s expected size could also create a storm surge of 5 to 10 feet above normal tides in places such as North Carolina’s Outer Banks and Chesapeake Bay, Sheets said.

From south to north along the East Coast, frenzied shopping and emergency planning peaked and then abated as Emily continued on a northwest path.

On Saturday, the victims of last August’s Hurricane Andrew in South Florida knew that they would be spared.

By mid-afternoon Sunday, the threat to Charleston, S.C., hard-hit by Hurricane Hugo in 1989, seemed to have passed. Still, some people got ready.

“People that went through Hugo know that after the hurricane there’s nothing left,” said George Deets, working at Ace Hardware in James Island, S.C., “so they’re stocking up and just trying to be prepared.”

Sheets said that predicting Emily’s path has proved to be “one of the most complex situations I’ve ever encountered”--due largely to a ridge of high pressure pushing south through the mid-Atlantic states. If high pressure blocks the storm to the north, Emily could turn more to the west.

Emily could also begin to move parallel to the coastline. In that case, the forces steering it would be tougher to read, and the storm itself would imperil millions more people as it moved toward New York and the heavily populated Northeast, Sheets said.

Hurricane Gloria in September, 1985, was such a storm. Although Gloria caused relatively little damage, it took three days to move up the East Coast and sent millions scrambling for safety.

Hurricane Andrew, the costliest natural disaster in U.S. history, left 250,000 people homeless, 35 dead and as much as $30 billion in damage. Hugo caused 27 deaths and $7 billion in damage.