Faced with the growing inevitability of the most forceful October storms in at least a generation, people from North Carolina to New England and as far west as Ohio did all they could Friday to get ready.

Emergencies were declared, line crews were summoned, shelters were prepared and command centers opened. People stockpiled food, bought generators and chain saws, taped windows against the wind’s blast, and prepared to hunker down as Hurricane Storm Sandy conspired with the jet stream and a nor’easter to deliver several days of misery and destruction to the most populated section of the nation.

The two big weather models that track storms came to a consensus Friday that the storm would turn inland somewhere to the east of the Chesapeake Bay and drench at least eight states as it drives across the Great Lakes into Canada. It is expected to turn into a blizzard before it gets there, dropping up to a foot of snow.

Sandy’s top winds diminished Friday, and the National Hurricane Center in Miami briefly downgraded it to a tropical storm Saturday morning before restoring it to a Category 1 hurricane — with sustained winds of 75 mph — a few hours later.

“[The storm’s loss of power] absolutely does not mean the threat to the eastern U.S. has decreased,” said Brian McNoldy of The Washington Post’s Capital Weather Gang. “Quite the opposite, in fact. It is forecast to reorganize and strengthen on its inevitable approach to the East Coast.”

Several factors combine to make this storm particularly dangerous.

Rain is expected to spread over much of the region Sunday afternoon as the leading edge of the storm advances toward land, and people with events planned then and in the days to follow said they were pondering canceling them.

The first of it may fall on thousands of runners and hundreds of departing horses, as the annual Marine Corps Marathon flows through the streets of Washington and, later in the day, the last of more than 500 horses leave Verizon Center after the international horse show.

“Right now, we’re going on with all of our events as planned. Runners will come rain, wind, whatever,” said Tami Faram, the spokeswoman for the marathon. “We’ll just have to wait and play that by ear.”

Jennifer Wood, with the horse show, said she hoped that the last of the horses and spectators would be gone before the worst arrives.

“Luckily, we don’t think we’re going to have much of an effect,” she said.

Gloria Garrett, who manages the Palisades Farmers Market every Sunday in Northwest Washington, said she wasn’t too worried about the storm. “I just
e-mailed everyone to be sure they have their weights” for their tents, said Garrett, who added that some shoppers might decide to stock up before the storm. “I think there might be up to a 20 percent uptick in sales.”

With the full force of Sandy expected to arrive sometime on Monday, school schedules were in jeopardy.

“We’re reminding people to check our Web site periodically just in case the weather becomes nasty,” said Phil Kavits, a spokesman for Prince William County Public Schools.

Officials with D.C. Public Schools also asked parents to check the school system’s Web site. “We are taking every step necessary to ensure that our buildings are protected throughout the storm and ready to open on time,” spokeswoman Melissa Salmanowitz said in a statement.

Public schools in Prince George’s County were previously scheduled to be closed Monday for a teacher workday, and if the storm holds its path, none of the region’s schools is likely to be open, although most said they will wait until Sunday to decide.

“A lot of it depends on which track the storm takes and when it hits,” said Dana Tofig, spokesman for Montgomery County Public Schools. “There really isn’t much we can do except wait to see what happens.”

Although school officials have a window that lets them delay their decision making, the rest of the officials and populace did not. Governors — including Virginia’s and Maryland’s — declared official states of emergency. District and state highway crews prepared to clear debris from roads. The region’s utility providers called on companies outside the area to send as much help as possible. Dominion Virginia Power asked to borrow 2,000 workers, while Pepco asked for 2,500 to be sent to the District and Maryland.

“This is a dangerous storm on many levels. Trees could be damaged by heavy rains and high winds, making them susceptible to falling,” said Melinda B. Peters, head of the Maryland State Highway Administration. “During the storm, travel conditions will be hazardous, and motorists should expect that there could be delays and detours for days after as crews clean up.”

Hurricanes are nature’s brawny beasts, accustomed to having their way with whatever they encounter. Sandy has all the size and power of a major hurricane, but it’s about to run headlong into a trap set by two rivals that may keep its wrath focused on the Washington region for 48 hours. The meteorological trap has been set by the jet stream, which is snaking south from Canada to hem in Sandy from the west, and a strong nor’easter standing in the way of the normal track that delivers hurricanes to a relatively harmless death in the North Atlantic.

Pepco, whose performance in responding to power outages has been criticized after recent storms, warned that hundreds of thousands of its customers may lose power it the storm lives up to expectations. “We’re hearing forecasts that we could see heavy sustained winds for up to 48 hours as this storm makes an agonizingly slow track across our overall system,” said Thomas H. Graham, the utility’s regional president. “If winds are too high, we will not be able to start restoration work until they die down, so it could be as long as even a day or two before our crews could safely start working to restore power.”

A slow-moving hurricane will provide more sustained rainfall, resulting in more flooding. Several counties sent crews out on Friday to vacuum storm drains.

“This is the benefit of having the time to prepare,” said Scott Peterson, spokesman for Prince George’s. “At this point, we have all hands on deck.”

Peterson said that there was major flooding in the county during Tropical Storm Lee last year.

Also preparing for a shock were mass-transit systems and airports, and airlines recognized that they were facing a situation that could snarl aviation for days after the storm had passed.

The three major commuter systems — Metro, the Maryland Transportation Administration and Virginia Railway Express — plan to continue normal operations until conditions require otherwise. “If conditions really deteriorate on Sunday, we may change that, but at this point, we’re proceeding,” Metro spokesman Dan Stessel said. The transit agency began placing sandbags around vent shafts and station entrances of the subway system. Crews had also begun checking pumping stations that will funnel water out of the stations, ensuring that drains were clear and that enough chain saws were available if there were downed trees. Also, additional rail and bus supervisors are being called in to work at control centers.

The Maryland Transit Administration began mobilizing emergency operations and maintenance workers, said spokesman Joe Sviatko. “As long as it’s safe, the goal is to keep everything open that we can during our normal operational hours,” Sviatko said. The agency has additional diesel trains available for MARC’s Penn Line, which typically uses electric trains, to try to ensure that there is MARC service Monday. MTA officials will assess the storm’s path Sunday afternoon to determine the extent of service available on the system’s buses, trains and light-rail system.

VRE is planning full service on Monday, barring any major weather-related problems. “Right now, we’re preparing as if we will run service like we have before,” said Mark Roeber, a spokesman.

VRE would likely cancel Monday service if the Office of Personnel Management announces that the federal government is closed, he said. Flooding or debris on the tracks could also snarl or cancel some VRE service.