A fierce storm that struck suddenly before dawn yesterday ambushed much of the East Coast, burying an unsuspecting Washington region under about a foot of snow and catching the federal government on its heels.

At daybreak, less than 10 hours after the rapidly developing storm over the Carolinas startled forecasters and confounded their new supercomputer, it had already dumped more than a half-foot of snow on Southern Maryland. Last night, the accumulation had reached 17 inches in Anne Arundel County, 14 inches in Fauquier County and 9.3 at Reagan National Airport--the heftiest snowfall since the blizzard of January 1996 dropped up to two feet on the region.

The driving snow and harsh winds showed no more mercy elsewhere on the East Coast. The storm socked Raleigh, N.C., with a record 20 inches, whitened the sands of Myrtle Beach, S.C., threatened tidal flooding along the Atlantic Ocean and disrupted air traffic over much of the country as airports, including the three in the Washington area, were forced to close. Aviation officials expected delays to ripple through today.

"This is the kind of storm likely to be remembered because it is so widespread," said Andy Woodcock, a meteorologist at the Washington-Baltimore office of the National Weather Service.

With flurries and drifting snow continuing to bedevil clearing efforts through last night, all major school districts in the region announced there would be no classes today. Federal offices in the area and some other government offices will remain closed today.

Those who went to sleep Monday night without watching the late television news were blindsided by the blinding snow. Although many people welcomed last Thursday's snow as a lark, they awoke yesterday to an onerous powder that was both deeper and earlier than predicted.

"Am I the only one who didn't know this storm was expected? I mean, how did I miss it?" asked Dana Sealy, of Cheverly. She had been falsely reassured by the early television news Monday and was mortified when she stared out from her bedroom window yesterday morning into a white abyss.

The Office of Personnel Management, initially doubting the severity of the coastal storm, announced at 5 a.m. that federal offices would remain open, only to reverse that decision two hours later after thousands of government employees had braved near-blizzard conditions bound for work.

The late call by OPM contributed to what police said was unexpectedly heavy traffic on area highways, already transformed in most cases to slick, single-lane trails. During the morning, police counted scores of minor accidents across the region and dozens of disabled cars marooned on highway shoulders and in snow drifts but reported no serious injuries.

"We were surprised how much traffic was out early, when it was still dark out," said Pete Piringer, spokesman for the Maryland State Police.

By evening, as snow continued to swirl, sparse traffic crawled along slushy main roads, and fresh snow remained unplowed on countless neighborhood streets.

Prospects for smooth travel this morning were grim, officials said. "I think it's fair to predict that the morning rush hour will be a bear," said Joan Morris, spokeswoman for the Virginia Department of Transportation. "How much of a bear depends on when the storm subsides and how many people are going to work."

Both Virginia Gov. James S. Gilmore III (R) and Maryland Gov. Parris N. Glendening (D) declared states of emergency, giving them power to deploy National Guard troops to help elderly or medical personnel stranded on the roads.

Across the region, schools, state and local offices, and colleges scurried to call a snow day. Public attractions, including the National Gallery of Art and the National Zoo, kept their doors closed. Even shopping malls did.

Area hospitals put out an urgent call for drivers with four-wheel-drive vehicles to help ferry medical personnel to work. Dave Miller, 35, an airline pilot with a canceled flight, answered the summons, shuttling doctors and nurses to Loudoun Hospital Center in his Ford truck. "I want them to be able to be there for other people," said Miller, of Leesburg. "It gives me something to do on a day I'd probably just be sitting home online."

The U.S. Coast Guard rescued four people from the Bay King, a 110-foot tugboat, when it broke loose from a barge it was towing and started taking on water near Cape Charles, Va. While a Coast Guard cutter searched for the runaway barge in swirling snow and nine-foot swells, authorities closed the Chesapeake Bay Bridge-Tunnel for an hour out of concern that it might be struck by the vessel, which finally ran aground.

Even the powerful were powerless in the face of nature. A reception honoring Maryland Comptroller William Donald Schaefer, expected to attract 1,200 guests, was postponed. Gilmore canceled his monthly radio call-in show on WTOP. A senior Chinese military delegation was forced to ride Metro from Washington to the Pentagon for a meeting on renewed military ties. A Senate hearing on global warming was canceled.

The nor'easter was particularly brutal in Southern Maryland, where an early coating of sleet was rapidly camouflaged by some of the region's heaviest snowfall. Main roads disappeared under drifts. White roads and the white horizon blended together, testing the best drivers.

Cliff Stathers cruised Route 235 in St. Mary's County in his red GMC pickup truck to tow several errant cars out of ditches. "If we did our work like the weathermen predict the weather," he asked, "would we still have a job?"

One of those who dutifully reported for his federal job was Colin Kendall, of Centreville, who rose at 5:15 a.m., bundled up in a parka and took a bus to Metro and then another bus to Walter Reed Army Medical Center, where he works as a computer security officer. Seven hours after he woke up, Kendall was among the grim clots of homeward-bound federal workers straggling off the trains at the Vienna Metro station.

"Somebody in OPM was really dumb on this one," Kendall said. "They should have made their decision much earlier. It was obvious when I got up that this was going to be a big storm."

Service on the VRE and MARC commuter rail systems was disrupted. Amtrak canceled all trains south of Washington and ran sharply reduced service between Washington and New York. Amtrak did, however, operate a first-class charter yesterday to return the New York Knicks home after their game against the Washington Wizards was canceled.

Metrorail managed to keep running but faced increasing delays as the snow mounted in evening hours. Metrobuses ran yesterday afternoon only on major roads.

The weather paralyzed the region's three commercial airports. Reagan National Airport remained closed all day, about three-quarters of flights at Dulles International Airport were canceled, and all flights were delayed at Baltimore-Washington International Airport.

Officials at all three airports said they expected it would take at least through today for airlines to accommodate the backlog of travelers and resume scheduled operations. "It's going to be a tough couple of days," said Betsey Sanpere, a BWI spokeswoman.

Long-distance bus travel also came to a standstill. Charles Wormley, a supervisor at the Greyhound terminal near Union Station, said Amtrak took some northbound passengers, while about 60 were given blankets so they could sleep on buses, which had their heaters on. In the terminal, about two dozen people were waiting at 10 p.m. Some had been there since 5 a.m.

Kareem Fortune, 24, was headed from New York City to South Carolina. "I'm tired. I'm mad. I'm ready to go home," he said as he sat in a chair in front of a pay TV and listening through headphones.

About 150 people were sheltered last night at the Central Union Mission at 13th and R streets NW, according to shelter supervisor David McElveen. They got a meal of beans and rice and could watch Christian movies. The shelter's nominal capacity is 110, but extra cots are brought in, and the mission won't turn anyone away.

In Virginia, VDOT sent about 800 plows and sand trucks onto interstates and other main highways shortly after midnight.

Maryland dispatched more than 2,000 plows, salt trucks and other equipment, redirecting equipment from the western part of the state to the Washington suburbs and other severely affected areas in the central and eastern sections, according to Fran Ward, spokeswoman for the State Highway Administration.

"Plow trains come through, and snow covers it again," she said. "It's a constant battle. We're keeping crews out there as long as we can."

D.C. deployed more than 200 snowplows and trucks to clear main thoroughfares. "The city has been slowed down by the storm, but we're not paralyzed," said Mayor Anthony A. Williams (D).

Area utility companies said they experienced few problems. Potomac Electric Power Co. reported scattered outages in fewer than 100 homes in Prince George's County and Anacostia early in the day but had power restored within a few hours. Virginia Power also had several hundred customers briefly without power in Alexandria, Warrenton and Leesburg.

Bell Atlantic officials said the phone system was severely taxed as thousands of Washington area residents stayed home, logging on to the Internet and using the phone to pass time or telecommute. Throughout the day, callers received "all circuits are busy" messages or rapid busy signals indicating that phone lines were filled to capacity.

While many officials and commuters wrestled with the mammoth storm, some embraced the whimsical weather.

On King Street in Alexandria last night, Marianne Smith, 40, bundled in black coat, black hat and black scarf, was walking--with the help of ski-pole-like exercise devices--from near the Potomac to the Masonic Temple so she could look down on the city. Her nighttime journey was more for the beauty than the exercise, she said. "It's just beautiful. It's so unusual, but I thought I might as well take advantage," the federal government employee said.

Anna Aurilio, a staff scientist at the U.S. Public Interest Research Group, did not take the day off and was glad she didn't. "I skied from Carter Barron to Foggy Bottom, and it was gorgeous. I saw three cardinals," said Aurilio, 36. Outfitted with a headlamp, she planned to ski home as well. "The thing about D.C. is they're not that good at snow removal, so it's great for skiing."

CAPTION: Snowplows work their way down Interstate 66 inside the Capital Beltway. By evening yesterday, sparse traffic was crawling along main roads.