Hurricane Sandy continued its angry advance toward the East Coast on Sunday, loaded with high winds and driving rain that threaten to cut power to millions and bring havoc for some of the nation's most densely populated areas.

The storm, centered about 250 miles southeast of North Carolina's coast, remained a Category 1 hurricane with a wind speed of 75 mph. according to the National Hurricane Center's latest report at 11 a.m.

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The hurricane center also reported that Sandy is expected to bring life-threatening storm surge flooding to the Mid-Atlantic coast, including Long Island Sound and New York Harbor.

New York Gov. Andrew Cuomo has ordered New York City's transit service to suspend bus, subway, and commuter rail service at 7 p.m. Sunday. The city's mass transit system is the nation's largest. The subway alone has a daily ridership of more than 5 million.

Winds are expected to be near hurricane force at landfall, which is now most likely to be somewhere along the New Jersey coast very early Tuesday morning. But the massive storm is forecast to hammer much of the eastern U.S., and more than 50 million people in the storm's path were preparing for its rage.

AccuWeather is reporting that Hurricane Sandy remains on track to become a historical storm, with places from Norfolk, Va., to Washington, D.C., to Boston bracing for catastrophic impacts. The worst is forecast to be Monday through Tuesday.

MORE: East Coast hunkers down as scary Sandy moves in

President Obama was monitoring the storm and working with state and locals governments to make sure they get the resources needed to prepare, administration officials said.

Governors from North Carolina, where heavy rain was began rolling in Sunday, to Connecticut declared states of emergency. Delaware ordered mandatory evacuations for coastal communities by 8 p.m. Sunday. An estimated 50,000 residents of Delaware's coastal communities were ordered to leave their homes under a mandatory evacuation ordered by Gov. Jack Markell.

Officials issued a mandatory evacuation for New York's Fire Island. About 200 permanent residents of the summer haven have until 2 p.m. Sunday to leave the island that officials say is prone to flooding. "It's a thin strip of land and it borders two sides of water," says Inez Birbiglia, spokeswoman person for the Town of Islip, which has partial jurisdiction over the area. "They need to evacuate so that resources during the emergency can be allocated to other needy places on the mainland."

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On Saturday evening, Amtrak began canceling train service to parts of the East Coast, including between Washington, D.C., and New York. Airlines started moving planes out of East Coast airports to avoid damage and adding flights out of New York and Washington on Sunday in preparation for flight cancellations on Monday.

Sandy took a short breather early Saturday and weakened into a tropical storm, but only for a couple of hours before it roared back to hurricane status.

It is expected to push heavy rains into most of the region by Monday. The storm's center is likely to make landfall somewhere along the New Jersey or Delaware coast late Monday or early Tuesday, according to computer forecasting models.

The storm's winds, rains and potential snow could cause widespread havoc. Weather forecasters predict up to 10 inches of rain in some regions, snowstorms in others and widespread wind damage that could down power lines.

The storm was expected to continue moving parallel to the Southeast coast most of the day and approach the coast of the mid-Atlantic states by Monday night, before reaching southern New England later in the week. High-wind watches and warnings are in effect for all the Mid-Atlantic states and southern New England.

If Sandy hits near New York City, as one weather model predicts, the storm surge will be capable of overtopping the flood walls in Manhattan, which are only 5 feet above mean sea level, according to Weather Underground meteorologist Jeff Masters.

Storm surge is the massive mound of water that builds up and is pushed ashore as a hurricane moves over the ocean. Sandy's storm surge may be higher than Hurricane Irene's, Masters said, and has the potential to flood New York City's subway system.

The storm's landfall along the Mid-Atlantic coast "would likely be a billion-dollar disaster," Masters says. He also noted that the full moon will occur Monday, which means astronomical tides will be at their peak for the month, increasing potential storm surge flooding.

The American Red Cross is readying shelters, volunteers and supplies to help coastal areas from Virginia to New England. "We want to make sure we're ready to spring into action as soon as we're needed," spokeswoman Anne Marie Borrego says.

The Red Cross has been shipping blood to hospitals in the affected region.

The Federal Emergency Management Agency has sent incident management teams to Connecticut, Delaware, Maine, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island and Vermont to help local emergency managers prepare for the storm and its aftermath. The agency also sent liaison officers to emergency operations centers in Maryland, Virginia, Washington, D.C., Pennsylvania, New York and New Jersey. The Defense Department has sent
officers to deploy with the FEMA teams to coordinate possible search-and-rescue missions.

"This is a big storm with potential impacts beyond coastal areas. Know your risks, have a plan and be prepared," FEMA Administrator Craig Fugate says. "Now is the time to update your family communication plans, check your supplies, and stay informed."

FEMA has stockpiled supplies, including generators, blankets, water and food, throughout the Eastern Seaboard and at military bases in the region, including Fort Dix in New Jersey.

National Guard soldiers have been mobilized in several states, including North Carolina, Virginia, and Connecticut.

In North Carolina, 75 members of the National Guard have been positioned around the state to provide emergency relief if needed, says Julia Jarema, a spokeswoman for North Carolina Emergency Management.

Soldiers in Raleigh, Tarboro, and Washington, N.C., may be called to hand out supplies, perform rescue missions or help with general operations.

National Guard soldiers and state troopers are taking pre-storm positions in Virginia. Contractors, including those who remove debris, have also been readied."We're about as ready as we're going to be able to be," Virginia Gov. Bob McDonnell says. "Our biggest concern remains that this will be a storm of lengthy duration."

The College of William and Mary in Williamsburg, Va., canceled Monday classes but promises students that food service will be operating no matter what.

In Connecticut, the Naval Submarine Base in Groton prepared to install flood gates and pile up sandbags to protect against flooding while its five submarines remain in port through the storm.

"Sandy could pose an enormous threat to major metropolitan areas in the Northeast, like New York City and Long Island, Atlantic City and Baltimore," says Howard Botts, vice president of CoreLogic, a research and consulting firm based in Santa Ana, Calif.

AccuWeather meteorologist Tom Kines says winds could have the biggest impact, causing widespread power outages. "You've got to be concerned since it's an area with such a large population," Kines says.

Storm surge remains one of the biggest threats from the storm: Data from CoreLogic shows that more than 261,000 homes valued at more than $80 billion are at risk from potential storm-surge damage in the coastal Mid-Atlantic states, assuming the storm hits the coast as a Category 1 hurricane.

"This will be a long-lasting event, with two to three days of impact," says James Franklin, branch chief of the National Hurricane Center. "Wind damage, widespread power outages, inland flooding and storm surge are all likely."

Sandy is gearing up for an assault from South Carolina to New England. Weather forecasters say the storm is likely to run into a cold front approaching from the Midwest, which could dump up to 2 feet of snow in parts of West Virginia and Virginia.

In the final weeks before the U.S. presidential election Nov. 6, the storm was presenting a challenge to the campaigns of President Obama and his Republican challenger Mitt Romney.

Romney scrapped plans to campaign Sunday in the swing state of Virginia and switched his schedule for the day to Ohio. First lady Michelle Obama canceled an appearance in New Hampshire for Tuesday, and Obama moved a planned Monday departure for Florida to Sunday night to beat the storm. He canceled appearances in Northern Virginia on Monday and Colorado on Tuesday.

The storm could also affect voting.Absentee voters lined up by the hundreds in Virginia on Friday to cast their ballots, some motivated by the fear that Tropical Storm Sandy may make it more difficult to get to a polling place.

"I think it ( the storm) just encouraged me to go ahead and turn up and vote rather than wait until later," voter Tania Sebastian says.

Early voting in Maryland and Washington, D.C., is underway, and some voters have found long lines.

Delaware was bracing for a threat rivaling the March 1962 nor'easter that has stood as the state's worst storm. Collin O'Mara, secretary of the Department of Natural Resources and Environmental Control, says Sandy could unleash record waves and tidal flooding along the coast."The potential on this is greater than the defenses that we have in most places," O'Mara says. "We're taking this as an extremely significant problem, probably the most significant we've seen in decades."

Insurer Allstate is expanding efforts to prepare, spokeswoman April Eaton says."We are currently rolling our catastrophe personnel, mobile claim centers and catastrophe response vehicles to Raleigh, N.C., for staging," she says. "Staging allows us to get our national catastrophe team members and units positioned in a safe place, but close to areas that may be impacted by Sandy.

"Once we see where the hurricane makes landfall, and authorities allow us in, we're able to move from the staging area or holding pattern and go into the heavily damaged communities to help Allstate customers begin the claim process."

Eaton says Allstate will send nine mobile claim centers to Raleigh, N.C., and Allentown, Pa.

The National Hurricane Center issued a tropical storm warning as far north in Florida as St. Augustine and parts of North and South Carolina.

Pepco, the electric company that provides service to Washington, D.C., and parts of Maryland, has activated emergency teams and begun scheduling workers who might have to assess damage, restore power and coordinate with other power companies in the region, spokesman Marcus Beal says.

"We're already making plans and working as if this is a definite event," he says.

In New Jersey, officials told people to be prepared for several days without electricity. Gov. Chris Christie declared a state of emergency. The emergency declaration will force the shutdown of Atlantic City's 12 casinos for only the fourth time in the 34-year history of legalized gambling there. Atlantic City officials said they would begin evacuating the gambling hub's 30,000 residents Sunday, busing them to mainland shelters and schools, and officials advised residents of flood-prone areas to stay with family or be ready to leave. Airlines said to expect cancellations and waived change fees for passengers who want to reschedule.

Workers at the Francis Asbury Manor assisted-living facility in Neptune Township are helping about 110 residents prepare for an evacuation at 10 a.m. Sunday. Most will be bused to a sister facility in Newton, says Jan Carrato, a spokeswoman for United Methodist Homes, which operates both facilities. Some will go to nursing homes inland and some will stary with relatives.

"We want to make sure we are connecting with everybody and that we will have a game plan in place if the storm requires us to respond," says Paul Shipman, a spokesman for the American Red Cross in Connecticut and Rhode Island. He added that volunteers have been called to be on alert.

Shipman encouraged iPhone and Android users to download the Red Cross' Hurricane app.

At least 43 deaths in Cuba, Jamaica and Haiti were in Sandy's wake, including a 4-month-old Cuban boy crushed when his home collapsed.

Opinions vary on the amount of damage the storm could cause. Mike Smith of AccuWeather Enterprise Solutions is expecting the worst.

"I expect the total damage (including loss to the U.S. economy) to be worse than Katrina," he says.

What's creating this monster? A combination of Hurricane Sandy and another storm over the eastern USA, writes meteorologist James Cisco of the Hydrometeorological Prediction Center in an online report.

The winds from Sandy, Cisco writes, will be "incorporated into a hybrid vortex over the Mid-Atlantic and Northeast next Tuesday." This "unusual merger ... should settle back toward the interior Northeast through Halloween, inviting perhaps a ghoulish nickname for the cyclone along the lines of 'Frankenstorm,' an allusion to Mary Shelley's gothic creature of synthesized elements."

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