Hurricane Irene bore down on North Carolina on Friday, tens of thousands of people evacuated and East Coast cities including New York braced for a weekend hit from the powerful storm.

Fifty-five million people are potentially in Irene's path from the Carolinas to Cape Cod. Tens of thousands of coastal residents were leaving their homes for safety, starting in east North Carolina that juts into the Atlantic ocean and where Irene is due to make its first U.S. landfall on Saturday.

This is a big, bad storm, North Carolina Governor Bev Perdue said. We are prepared for the worst, praying for the best ... we are ready, she told CNN.

Coastal communities from the Carolinas to New England, stocked up on food and water and tried to secure homes, vehicles and boats. States, cities, ports, hospitals, oil refineries and nuclear plants activated emergency plans.

Forecasters expect that after hitting North Carolina's eastern coast as a powerful, broad hurricane on Saturday, Irene will then rake up the densely-populated U.S. eastern seaboard to New York, America's most populous city of more than eight million inhabitants, and beyond.

Flooding, flash flooding and power outages will impact a lot of folks, Federal Emergency Management Agency Administrator Craig Fugate told CNN. The capital was also expected to feel wind and rain impact.

Extensive flight and rail service cancellations were expected.

Hurricane warnings and watches were in effect from North Carolina northwards as far as Massachusetts. Cities covered by these alerts included New York City and Boston.

EQECAT, a company that helps the insurance industry predict disaster damage, said Irene's forecast track represented one of the worst-case scenarios for the United States. It was one of the biggest storms to threaten the northeast in decades.

I filled my tank up with gas in case I need to leave in a hurry or something, and get a lot of food supplies, taking everything out of my yard ... anything that can fly into a window, said Patricia Stapleton of Newport, North Carolina.

Irene weakened slightly early on Friday -- to a Category 2 hurricane from a Category 3 on the five-step Saffir-Simpson scale -- but still was packing winds of up to 110 miles per hour.

At 8 a.m. EDT, its center was about 375 miles south-southwest of Cape Hatteras, North Carolina, moving north.

NORTHEAST CITIES IN PATH

Some re-intensification is possible today and Irene is expected to be near the threshold between Category Two and Three as it reaches the North Carolina coast, the U.S. National Hurricane Center said.

Coastal evacuations were under way in North Carolina and were ordered for beach resorts in Virginia, Delaware and Maryland. Airlines began to cut flights at eastern airports, made plans to move aircraft from the region and encouraged travelers to consider postponing trips.

All the major metropolitan areas along the northeast are going to be impacted, National Hurricane Center Director Bill Read told Reuters Insider. Being a large hurricane, tropical storm-force winds will extend far inland.

Virginia Governor Bob McDonnell urged residents to seek shelter by Friday night, before the winds kick up.

Saturday is going to be a horrendous day for travel. There will be roads and bridges closed, he said.

Anticipating severe storm damage in North Carolina, U.S. President Barack Obama declared an emergency on Thursday, authorizing federal aid to support that state's response. The governors of North Carolina, Virginia, Maryland, Delaware, New Jersey, New York and Connecticut also declared emergencies.

Even if the center of Irene stays offshore as it tracks up the coast, its heavy winds and rain could lash cities like Washington, Baltimore, Philadelphia and New York and knock out power, forecasters said.

Irene will be the first hurricane to hit the U.S. mainland since Ike pounded Texas in 2008.

NEW YORK PREPARES

New York Mayor Michael Bloomberg said the city was bracing for storm conditions and flooding starting on Sunday.

He urged residents of vulnerable areas to move to safety on Friday because the mass transit system, the nation's biggest with 8 million passengers a day, may have to shut if flooding or high winds endanger its buses, subways and commuter trains.

Many New Yorkers do not have cars, so mass transit could be vital in evacuations.

Long Island, the populous area that extends about 100 miles east into the Atlantic Ocean from New York City, could be hit hard if Irene stays on its current track.

In Washington, Irene forced the postponement of Sunday's dedication ceremony for the new memorial honoring civil rights leader Martin Luther King Jr. Tens of thousands of people, including Obama, had been expected to attend.

Flooding from Irene killed at least one person in Puerto Rico and two in the Dominican Republic. The storm knocked out power in the Bahamian capital Nassau and blocked roadways with fallen trees.