Worried about possible disruptions in basic services caused by the Y2K computer glitch, many Americans descended upon stores yesterday to purchase bottled water, batteries, candles, canned food and other supplies. But merchants said their inventories remained plentiful and few customers appeared to be hoarding products.

Some banks and gas stations also reported increased consumer demand, but officials continued to express confidence in their reserves of cash and fuel.

"We're definitely seeing customer activity that is greater than normal when it comes to bottled water, batteries, flashlights, portable lanterns, packaged foods and baby formula," said Shawn Kahle, a spokeswoman for Kmart Corp. "But thus far, there's been no panic."

Across the Washington region and the nation, people appear to be preparing for the "millennium bug" as if it were a short-but-severe winter storm -- the metaphor that government officials have long used to describe the glitch's possible impact.

"I'm 99.9 percent sure nothing is going to happen," said Jeff Waters, a contractor in Fairfax, loading a case of bottled water into his shopping cart at a Costco Wholesale store in Merrifield. But if something does happen and he is not prepared, Waters said, he would "feel real stupid."

In supermarkets and discount stores yesterday, Y2K worriers and New Year's Eve party planners collided in the aisles. Most customers, however, engaged in measured purchasing, often buying only a few gallons of water, a couple of packages of batteries and some canned food. Many eschewed more extreme measures such as topping off their gas tanks, withdrawing large sums of cash or filling shopping carts with supplies.

"There doesn't seem to be any run on the pumps," said Harry Murphy, a spokesman for the Service Station & Automotive Repair Association. A Bank of America Corp. spokesman said cash withdrawals this week have been at "normal levels for the holiday season."

The absence of hoarding is a particularly reassuring sign for government and business leaders, who have long worried that panicky consumers could cause more chaos than any computer failures.

"A big concern was that people would go into stores and buy the place out," said Cathy Hotka, the vice president for information technology at the National Retail Federation. "We're happy that people are being prudent about their preparedness."

Technology specialists, however, caution that demand for food, water, money and gasoline could dramatically increase this afternoon and evening if severe Y2K problems strike Asia and Europe and are conveyed by live television news reports. And in the United States, the readiness of some critical computer systems, particularly those that control the nation's air traffic and power grid, could be clear as early as 7 p.m. EST because their internal clocks are set to Greenwich Mean Time, which runs five hours ahead.

In other Y2K developments, the government began gearing up to watch for any Y2K disruptions, with a White House command center starting round-the-clock operations last night. At 20 air-traffic control centers, technicians installed what the Federal Aviation Administration called "a very, very minor" Y2K software patch in computers that handle high-altitude jetliner traffic.

Starting just before midnight tonight, many transportation systems, from elevators in high-rise buildings to subway cars and Amtrak trains, will pause for several minutes so technicians can check for glitches. An Amtrak spokesman called the shutdown "just a precaution."

That's just how many consumers characterized their purchases of food and water yesterday.

At the Merrifield Costco, Claire Stalnaker, 32, piled her cart high with three cases of Crystal Geyser water (28 bottles apiece), a case of fireplace logs and a dozen boxes of macaroni and cheese as well as other nonperishable foodstuffs.

Stalnaker, who lives in Fairfax, said she's not worried about any possible Y2K problems this weekend, but she was spending the $500 that her worried mother had given to her and each of her five siblings, along with a list of recommended Y2K supplies that her mom had pulled off the Internet.

"I don't think there's any reason for concern," said Stalnaker, who has two young children. But, she said, "I might as well get things that I will use."

At Home Depot stores across the nation, sales of flashlights, batteries, kerosene heaters and generators have been brisk. But company officials trace the demand to bad weather and a healthy economy.

The Y2K bug is "becoming a nonevent of the millennium," spokesman John Simley said. "The power supply is safe. Certainly we're not the kind of company that's going to use [Y2K concerns] to sell to people."

But at the Home Depot on Pickett Street in Alexandria, there is a giant promotional center in front of the store that includes batteries of every size, while generators, flashlights and packaged fireplace logs are stacked by checkout lanes. While customers have not been snapping up generators, battery sales have about doubled over last year, a store manager said. Earlier this week, the store ran out of propane tanks.

At a Giant supermarket in Fairfax City, bottles of water have been stacked near the cashiers, while candles, Sterno canned fuel and matches are prominently displayed in another part of the store. One shopper there, Olivia Aguirre, 27, said she has spent more than $100 in the past two days to prepare for Y2K, purchasing "baby food, water and cans of food." Pausing for a moment to think, she continued her list: "Bread, toilet paper, napkins, baby wipes, diapers, candles and flashlights."

Aguirre said she was stocking up because "we don't know what will happen."

At the Giant in Van Ness, employees yesterday decided to dismantle a special Y2K display that for weeks had featured batteries, flashlights, candles, bottled water and Sterno, because the store didn't have enough of the stuff left to make a decent display.

Kmart said sales of bottled water and baby formula are up about 40 percent compared with this time last year, while the vice president of Costco's mid-Atlantic region pegs the jump in demand for such products at between 50 percent and 100 percent. And at 7-Eleven stores, sales of size C Energizer batteries -- typically used in flashlights -- were 412 percent higher than normal in the week of Dec. 20, company spokeswoman Margaret Chabris said.

All has been quiet at 7-Eleven's gas pumps, however. "We haven't seen an increase in gas sales," Chabris said. "We think that's coming."

To prepare for that, oil companies have been moving supplies of both heating oil and gasoline to retail outlets and distribution centers so that dealers will have more than usual on hand, said Jay Hakes, chief of the federal Energy Information Administration.

The same phenomenon appears to be occurring at banks, where cash reserves have been dramatically increased to handle an anticipated -- but still nonexistent -- rush of withdrawals. At Riggs Bank on Wisconsin Avenue and M Street NW, for instance, a steady stream of customers flowed past the steel-gated doors yesterday morning, but the business seemed to have more to do with payday at nearby Georgetown University than Y2K fears.

"I haven't done anything. My mother gave me a bunch of water and canned goods," said George Montgomery, 49, a mailroom manager at the university, "so I know where I can go for more if anything happens."

Some of the most frenetic Y2K preparations are occurring in the region's outer suburbs, where residents are more familiar with storm-related power and phone outages. In the southern Maryland community of Charlotte Hall, shoppers have exhausted the True Value hardware store's supply of five-gallon kerosene cans. Shoppers who planned on storing either kerosene or water in the cans are now buying up gasoline jugs for water storage, said manager Marty Rudman.

At the Southern States farm supply store in Leesburg, customers lined up yesterday to stock up on extra fuel for heaters and grills. The store has been busy all month, said clerk Rose Peyton, selling more than 3,000 gallons of propane.

The last of the kerosene heaters and cans to hold the fuel flew off the shelves Tuesday. "People are buying four or five cans at a time instead of just one," Peyton said.

Elaine Graham, 46, of Lovettsville stopped by the Southern States yesterday to buy fuel for her grill "just in case." Then she swung over to the nearby Giant for three extra gallon jugs of water.

And if that runs out?

"I have plenty of wine at home," she said, "so I'll be fine if anything happens."

Washington Post staff writers Stephen Barr, Maria Glod, Annie Gowen, Spencer S. Hsu, Martha M. Hamilton, Raja Mishra, Jacqueline L. Salmon, Stephanie Stoughton and Philip P. Pan, Liz Leyden in New York, and special correspondent Khiota Therrien in Seattle contributed to this report.

Road Closings

Closed until 11 p.m. Jan. 2:

Constitution Avenue between 9th and 14th streets

12th St. Tunnel northbound

12th St. between Independence and Pennsylvania avenues

Today

Tenth and 11th streets NW, between Constitution and Pennsylvania avenues (until 7 a.m. Jan. 2)

Henry Bacon Drive between Lincoln Circle and Constitution Ave. (until 6 a.m. Jan. 1)

Tomorrow

Ellipse: 16th St. at entrance to the Ellipse; ingress roadway at 15th St.; E St. at Ellipse entrance; and E St. between 17th and 15th, (6 a.m. until 6 p.m. Jan. 1).

West Potomac Park: 23rd St. at Independence Ave. and Inlet Bridge (Ohio Dr. near Jefferson Memorial) (6 a.m. until 2 a.m. Jan. 1).

Memorial Bridge: Ramp from southbound GW Parkway to Memorial Bridge; ramp from Rte. 27 (Washington Blvd.) to Memorial Bridge; Parkway Drive; the ramp from Ohio Drive to Lincoln Memorial Circle; 23rd St. and Constitution Ave. ( 11 a.m. until 2 a.m. Jan. 1).

Theodore Roosevelt Bridge: (midnight Jan. 1 until 1:30 a.m.).

15th St., Constitution to Independence avenues.

(6 a.m. to 6 a.m. Jan. 1).

Memorial Bridge/Lincoln Circle: (11 a.m. until 1 a.m. Jan. 1).

E St., 15th to 17th

(6 a.m. until 4 a.m. Jan. 1).

14th St., Constitution to Independence (11:30 p.m. until 12:30 a.m. Jan. 1).

7:30 p.m. today -- 1:30 a.m. Jan. 1:

Independence Ave., 14th St. to 23rd St.

17th St., New York Ave. to Constitution

18th St., E St. to Constitution Ave.

19th St., E St. to Constitution Ave.

20th St., E St. (south) to Constitution Ave..

21st St., E St. to Constitution Ave.

C St., 23rd St. to Virginia Ave.

22nd St.,

Constitution Ave. to C St.

23rd St.,

Constitution Ave. to E St.

7:30 p.m. today -- 2 a.m. Jan. 1:

Rock Creek Parkway: Rock Creek Parkway south of Virginia Ave.; the ramp from Potomac Freeway at the Kennedy Center; Kennedy Center Gates at Rock Creek Parkway.

Independence Ave.: Between 14th and 23rd streets, East Basin Drive at Ohio Drive.

Constitution Ave.: Between 14th and 23rd streets, entrance to the 16th Street Oval.

George Washington Parkway: Northbound at Rte. 395; south-bound from the ramp to Washington Blvd. to the ramp to northbound 14th St. Bridge (Rte. 395 North).

Parking restrictions for today:

On 23rd St. from Constitution Ave. to Washington Circle

On 17th St. from Constitution Ave. to H St.

On 14th St. from Constitution Ave. to F St.

On Penn. Ave. from 15th to 3rd.

On Independence Ave. from 14th to 3rd.

At 16th Street Oval (from 6 a.m. until 6 a.m. Jan. 1).

On Mall between 7th and 14th (from 9 a.m. until 9 a.m. Jan. 1).

The Ellipse (from 6 a.m to 6 a.m Jan. 1).

Hains Point closed all day (not shown on map).