Hurricane Sandy, hundreds of miles wide and gaining speed off the New Jersey coast, is moving so fast that forecasters predicted that it would make landfall by 6 p.m., hours ahead of earlier expectations, and cut a massive swath of destruction toward Philadelphia.
In Philadelphia, where tens of thousands of people have fled flood-prone neighborhoods in fear of a direct hit, Mayor Michael Nutter urged residents to stay inside and not be fooled by the relatively calm winds and rain that soaked the city all day.
"It's coming," Nutter said in an afternoon news conference. "The fact that Philadelphia is dead on in the path, that it is not only slow moving but may hover over us for a while, is reason to take this very seriously."
NBC10's Glenn "Hurricane" Schwartz said Sandy's wind speeds had increased to 90 mph, making it nearly a Category 2 storm, and was traveling toward land much more rapidly - at 28 mph - than it was on Sunday.
"This storm is moving so fast that it is very close to landfall right now," Schwartz said a little after 3 p.m.
As he spoke, the storm was about 60 miles from Atlantic City, making the next few hours the most dangerous along the coast, forecasters said. Sandy's hurricane-force winds extended up to 175 miles from the center - and tropical storm-force winds even farther - which means that its impact will be felt across the Northeast in the form of potentially deadly storm surges, massive flooding and widespread power outages.
The leading winds were so bad that NBC10's Lu Ann Cahn was having difficulty staying on her feet just outside Atlantic City.
Parts of Atlantic County are under five feet of water and there is significant flooding in Cape May and Ocean counties.
Water levels are expected to rise by 4 to 8 feet in coastal areas as the storm hits.
Tens of thousands of people across the region were already without power at 3 p.m., most of them in South Jersey.
New Jersey Gov. Chris Christie warned residents to stay home and off the roads. He also said that residents of the barrier islands who failed to evacuate on Sunday had made a mistake.
"If some of the high tide water recedes this afternoon and you see a way to get off the barrier islands, get off the barrier islands," Christie said. "If you don't then you have to shelter yourself in your home on the highest floor."
If anyone is traveling on local roads, they're in for a terrible commute. For example, the Garden State Parkway is closed from mile marker zero to mile marker 63.
The city shut down government buildings and schools on Monday and the closures would continue Tuesday.
Wind gusts of 40-60 mph are expected between 1 p.m. Monday and 6 am. Tuesday. The heaviest rain, 4-8+ inches will fall between 6 a.m. and 9 p.m. on Monday. The worst of coastal flooding is expected between 8 a.m. and 8 p.m. on Monday.
Wind speeds will increase Monday night, when the storm's impact will peak.
Sandy has already caused more than 60 deaths in the Caribbean.
President Barack Obama has signed an emergency declaration for New Jersey. The declaration will allow the state to request federal funding and other assistance for actions taken in advance of the massive storm
The rain and wind won't diminish until Wednesday morning, Schwartz said. That's two full days of blunt-force hurricane winds and rain, which is likely to cause severe flooding and widespread power outages.
The National Weather Service said Sandy would cause "life-threatening" storm surges along the mid-Atlantic coast.
Jersey Shore officials ordered a mandatory evacuation of barrier islands from Sandy Hook to Cape May, including Atlantic City casinos.
Officials warned that as roads flood with 3 to 4 feet of water and power lines fall, anyone who chooses to stay on the islands may not be within reach of rescue crews.
Schwartz predicted that, because the storm will linger over the area for so long, it will have a more devastating impact than what Hurricane Irene delivered in September 2011.
"Technically it's going to be the same intensity as Irene ... but (the effects are) going to be way worse than that, especially at the coast," Schwartz said.
With Sandy arriving during a full moon, coastal flooding may reach record levels. That means potentially worse conditions than the 1962 nor'easter that smashed Long Beach Island, Schwartz said.
Nutter declared a state of emergency for Philadelphia that went into effect at 5 p.m. on Sunday until 5 p.m. on Tuesday. He has issued evacuation orders for flood-prone areas of the city.
The Red Cross has set up shelters around the region for those forced to leave their homes.
SEPTA, which stopped service early Monday, said it would not consider resuming service until after Tuesday morning, when crews would try to determine whether it was safe. Check SEPTA's website for the latest.
Philadelphia schools, which canceled Monday classes, will remain closed on Tuesday, as will other area schools and offices.
Regular Amtrak service is not expected to resume until at least Wednesday.
All flights in and out of Philadelphia International Airport were canceled for Monday. It is unclear when flights will resume.
Sandy is expected to impact an estimated 50 to 60 million people along the eastern United States, according to the U.S. National Oceanic and Atmospheric Administration.
As Sandy moves across land, it is expected to slow down as it pulls in moisture from the Atlantic, triggering very heavy rain.
Sandy will then take a turn up to the north and east Wednesday and Thursday, wrapping around cold air on the backside of the storm. Heavy snow could develop west of the Philadelphia area.
"These are going to be winds that are sustained," Pennsylvania Gov. Tom Corbett said. "Especially when the ground is saturated, there's the potential for trees to come down ... for power lines to come down."
The governor added that residents should "be prepared to stay in your homes for an extended period of time ... perhaps without power or water."
A coastal flood warning is currently in effect for the Jersey Shore and Delaware beaches. A coastal flood watch is in effect for areas surrounding the Delaware River. A flood watch is in effect north and west of Philadelphia. A high surf advisory is in effect for the Jersey Shore and Delaware Beaches. Finally, a high wind watch is in effect for the entire area.
All of these watches and warnings are in effect until late Monday or until the storm passes.
Stay with NBC10 for continued updates on the storm.