Hoyt Scott, left, rings up a few bags of snowmelt for customer Stephanie Lyon in W.S. Jenks hardware store on Jan. 20 in Washington as citizens seek snow fighting supplies ahead of a potentially historic winter storm. (Bill O'Leary/The Washington Post)

Tick, tick, tick . . .

Maybe you heard there’s a blizzard coming.

A huge one. Historic, even.

And time is running out.

“People are buying a lot of eggs and a lot of milk and bread and water and toilet paper, too,” Jaswinder Bhopal, a Giant supermarket manager in Arlington, said Wednesday afternoon as shoppers swarmed the aisles.

A snowstorm headed toward Washington, D.C, and the Mid-Atlantic is expected to last 36 hours between Friday and Sunday. Capital Weather Gang's Angela Fritz has your forecast and snow accumulation predictions. (Ashleigh Joplin/The Washington Post)

“I already went to one store,” said Carla Wright of Bethesda, in a crowded Safeway near her home. “I got a lot of pasta, stuff for soup. . . . I have enough food for, like, a week.”

Tick, tick . . .

“We have been selling a lot of shovels, anti-ice, flashlights and sleds,” manager Kristy Peterkin said in Ayers Variety and Hardware in Arlington. “Those are the main four things. We have sold about a fourth of our supply of sleds.”

With an array of computer models in agreement that a massive storm will pummel the Mid-Atlantic this weekend, the National Weather Service on Wednesday issued a Blizzard Watch for the Washington area, citing the likelihood of crippling snow accumulations and powerful winds.

“Potential life-threatening conditions [are] expected Friday night into Saturday night,” the Weather Service warned.

The snow is predicted to begin falling here in the late morning or early afternoon Friday, with the worst of the storm probably occurring overnight Friday into Saturday, The Washington Post’s Capital Weather Gang reported. “For the immediate D.C. metro area, we’re thinking 12 to 20 inches, and that forecast can certainly be adjusted upward as the storm approaches,” said Capital Weather Gang meteorologist Angela Fritz.

Larry Middleton buys the last snow shovel at W.S. Jenks hardware store in Washington as citizens seek supplies ahead of a potentially historic winter storm. (Bill O'Leary/The Washington Post)

“The data is unwavering that this will be a major winter storm for the Mid-Atlantic,” Fritz said. “Add 40 mile-per-hour wind gusts on top of that, and you have prolonged periods of whiteout conditions when travel will be impossible.”

And she said “Everything we’ve seen tells us it’s going to be a long haul,” meaning possibly 36 hours of falling snow, from midday Friday to Sunday morning.

The nation’s capital and its suburbs, of course, are getting ready. But is the Washington area ever, truly, ready for snow?

Even a modest accumulation of snow Wednesday evening led to treacherous commutes, numerous accidents and infuriating delays, setting the region on edge as it prepared for the major storm to come.

“I have snow shovels, but I need to get some anti-ice,” said Stacey Rhodes of Arlington, braving the throng at Bhopal’s Giant. “Snow is fine once or twice a year. But I am hoping this will be it, then it will be like spring by early February.”

At the Aldie Country Store, in western Loudoun County, manager Varun Parti said the snow will mean no smoked chicken or ribs for customers because the store’s smoker is outdoors. But there will be plenty of antifreeze, wiper fluid and rock salt, he said.

“Thanks to Almighty, we were well prepared for it,” Parti said.

As of late Wednesday, Washington-area school systems had not decided whether to cancel Friday classes. But Arlington officials urged families “to make alternative child-care arrangements now in case schools need to close.”

The University of Maryland announced that it would be closed Friday through Sunday.

And a chorus of government leaders throughout the region implored residents to brace themselves for a potentially devastating weather event.

“State agencies are coordinating all available resources to prepare to clear roads and manage incidents that may be caused by this significant storm,” Maryland Gov. Larry Hogan (R) said in a statement. “Before the storm hits, make sure you have supplies at home and communications devices charged. Be a good neighbor — check on relatives, friends, and those who may be more vulnerable to cold and a big winter storm.”

Northern Virginia has 340,000 tons of salt, 95,000 tons of sand and 576,000 gallons of liquid road treatment at the ready, the Virginia Department of Transportation said. Maryland and the District said they are similarly prepared.

“The big challenge is neighborhood streets,” said VDOT spokeswoman Jennifer McCord, echoing statements by other officials in the region. “We have an infinite number of neighborhoods. There are more narrow streets so there are certainly more obstacles to deal with.”

The Weather Service forecast said the storm could be comparable to three enormous ones in the Washington area: the blizzard in January 1996, the Presidents’ Day storm of February 2003 and the February 2010 storm that came to be known as Snowmageddon.

The District said it has recruited and trained more than 1,000 people to shovel snow for elderly and disabled residents, said Michael Czin, spokesman for Mayor Muriel E. Bowser (D), who met Wednesday with the heads of city agencies to discuss preparations.

Like other power companies, Pepco said a storm as big as the one predicted for this weekend could cause havoc for electric customers.

“Our crews are poised and prepared,” said Vince Morris, a spokesman for Pepco, which has 2.3 million customers in Maryland and the District. “We hope there are no outages, but it’s not unrealistic to think we’ll have some.”

Metro spokesman Dan Stessel said the transit agency began planning for the storm early this week and intends to issue a detailed service advisory Thursday, including specifics on how the transit system will operate Friday for workday commuters.

He said Metro managers have been consulting with officials in the District, Maryland and Virginia and with the federal Office of Personnel Management. Any service changes will hinge partly on whether government offices will be open Friday, he said.

Although Metro intends to provide as much weekend service as it safely can, Stessel said, its main focus will be on “restoring normal service as quickly as possible after the storm,” meaning for Monday’s start of the workweek. That goal is more important than making full service available at the weekend height of the storm, he said.

As a rule of thumb, according to Metro’s website, the rail system “can operate very close to a normal schedule in a snowfall of four to six inches,” although trains tend to become crowded as travelers abandon roadways for public transit.

However, “Metro’s focus shifts when blizzards are predicted and snow accumulates beyond eight inches. . . . For safety reasons, as well as to preserve our railcars and allow for faster recovery after the storm, Metro may suspend above-ground rail service in a major snowstorm and serve only underground stations.”

Bus systems across the region, including Metro’s, said they will operate as road conditions allow, with many routes likely to be affected.

Most airlines have lighter schedules on Saturdays, meaning the storm probably won’t disrupt as many travelers as it would have during the workweek. Reagan National Airport, for example, handles about 850 flights on an average Friday, compared with 550 on a typical Saturday. But that’s of little consolation to Saturday ticket holders. Many airlines have already relaxed cancellation penalties and are issuing travel waivers to allow travelers to re-book their weekend flights.

Meanwhile, an Amtrak spokesman said the railroad would have extra workers on duty during the weekend and warned of possible “service adjustments” in the Northeast Corridor, meaning delayed or canceled trains, if the snow becomes unmanageable.

Like many other transportation officials, the spokesman, Mike Tolbert, issued a caution: “Anyone planning to travel during the storm is urged to allow extra time and be extremely careful in and around stations, on platforms and onboard trains.”

He said Amtrak will “strategically position diesel locomotives and on-track maintenance equipment in designated locations” along the Northeast Corridor in case falling trees or limbs damage the overhead electrical wires that power trains in the region.

“We put independent contractors on standby to quickly respond to reports of trees or limbs down along the right-of-way,” Tolbert said, adding that additional “mechanical, engineering and operations forces” also will be mobilized.

In Maryland’s Frederick County, Chloe Divel and her family were making plans Wednesday to keep their Ingrams Diner open through dinner Friday — and to open again at 6 a.m. Saturday. The restaurant is located beside a highway, and hungry road workers might want some chipped beef.

“It’s usually served on toast or on top of home fries,” Divel said. “But you can get it on pancakes. Some people get it on french fries.”

She said: “Our state highway guys. . . . They count on us.”

Lori Aratani, Ashley Halsey, Michael Laris, Luz Lazo and Faiz Siddiqui and contributed to this report.