HARRISBURG — Emergency management authorities urged Pennsylvanians on Friday to prepare for a potentially dangerous super storm that could pound the state with damaging winds, several inches of rain and maybe snow, possibly leading to power outages.

As Gov. Tom Corbett declared a disaster emergency, residents were told to stock their homes with enough batteries, water and food for three days in light of the monstrous, slow-moving mayhem predicted to strike the mid-Atlantic early next week.

The brewing weather system involving Hurricane Sandy is expected to pummel the East Coast harder than Hurricane Irene, which last year left hundreds of thousands of Pennsylvanians without power and eventually led to historic flooding.

In Philadelphia, the mayor told residents of flood-prone neighborhoods to be packed and ready to leave by Sunday afternoon.

Rain is predicted to begin falling in the city Sunday evening, he said, with the heaviest downpours starting Monday night.

“Do not wait until Monday to try to figure out what to do,” Mayor Michael Nutter warned, telling those in potential danger to make plans to stay with family or friends.

Sandy is expected to merge with a wintry front to create a mess that some have dubbed “Frankenstorm.” The entire Eastern region will be hit with steady, strong and damaging winds and rain for several days, according to federal forecasters.

Western Pennsylvania could get snow.

On Friday evening, Corbett activated the state Emergency Operations Center and authorized the transfer of $5 million in surplus funds to pay for disaster-related expenses. The disaster declaration also allows the Pennsylvania National Guard to be activated, if needed.

The move came just hours after Corbett toured an automotive carpeting plant in Bloomsburg, a central Pennsylvania town devastated last year by flooding spawned by Irene and the remnants of Tropical Storm Lee.

“We are doing everything we can,” Corbett said of preparations for the super storm. “We are gearing up and getting ready to go.”

A line for generators, more than 100 strong, snaked out the door and into the parking lot Friday evening at the Cabela’s superstore along Interstate 78 in central Pennsylvania, not far from some areas hit hard by Irene last year.

Bloomsburg resident Doug­las Jumper, whose first floor took on nearly 5 feet of water during the catastrophic flood in September 2011, was tying down his patio furniture on Friday and moving items in his wood shop to higher ground.

He choked up as he described the long, slow recovery from last year’s flood – and contemplated the possibility of yet more storm damage.

“I’m tired. I am tired,” Jumper, who turns 58 on Saturday, said through tears. “We don’t need this again.”

Across the street, Patrick and Heather Peters pulled into the driveway after a fruitless, multi-store search for a generator.

Their consolation prizes: A kerosene heater, 12 gallons of water, paper plates, batteries, flashlights and the last lantern on Walmart’s shelf.

They’ve also rented a U-Haul for Sunday and plan to move as many items from their home as possible and head to his mother’s house if the forecast is bad enough.

“I’m not screwing around this time,” Heather Peters said.

Philadelphia officials said the city could see record coastal flooding along the Delaware and lower Schuylkill rivers. Officials warned of 3 to 6 inches of rain between Sunday and Tuesday in central Pennsylvania, leading to possible flooding along tributaries of the Susquehanna River.

In Union County, where parts of Lewisburg flooded last year, emergency management coordinator Michelle Sanders noted the growing season is over – meaning there’s less vegetation to soak up moisture.

“There might be more runoff, so a potential of flooding is there,” she said. Predicted winds of up to 50 mph also could stress trees that haven’t shed their leaves, she noted.

Local officials throughout the state urged residents to clear leaves from neighborhood storm drains and to secure any outdoor decorations that could become projectiles. Allentown postponed its Halloween parade, one of many events being canceled or delayed by the forecast.

Amtrak and the Southeastern Pennsylvania Transportation Authority are monitoring the storm and preparing to deal with downed trees and wires.

Alvin Henderson, the acting chief of Allegheny County Emergency Services, which includes Pittsburgh and 130 surrounding municipalities, said the biggest question is not knowing what to prepare for. The storm’s track remains uncertain.

“One thing’s for sure, we have a lot of uncertainty,” he said.

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