The massive Valentine's Day sleet and ice storm that triggered the closure of most schools and many local governments in the Washington area today left one teenager dead, nearly 125,000 homes and businesses without power and prompted weather forecasters to predict an icy commute tomorrow morning.

A 15-year-old girl from rural Bluemont -- in western Loudoun County -- died after being struck by part of a falling tree. Police said the girl, who was not named, was walking in the front yard of her residence around 3 p.m. when a strong gust of wind broke off a portion of the tree. She was taken to Inova Loudoun Hospital, where she was pronounced dead.

The death came as thousands of Washington-area residents -- mostly in Maryland's Anne Arundel, Prince George's and Charles counties -- face the possibility of a night without electricity. Temperatures are expected to dip into the mid-teens tonight.

"It'll be windy overnight, so wind chills will be near zero between midnight and 6 a.m.," National Weather Service meteorologist Andy Woodcock said. "So people with power outages will have to dress warmly or go to a shelter. I'm nervous because we always hear of people using hibachis in their homes and causing a fire."

Don't expect any new ice tonight, Woodcock said. But the freezing rain that made roads and sidewalks treacherous today will not be completely melted by morning, he said. "So there will be icy spots on the roads and people can expect delays," Woodcock said.

Officials in Prince George's, Anne Arundel andCharles counties opened shelters{vbar} for people who do not have power at home.

Anticipating a rough morning commute, three county school systems--in Loudoun, Fairfax and Montgomery--have cancelled tomorrow's classes.

The overnight storm, which prompted a two-hour delay in the opening of the federal government today, created delays for commuters this morning, as Metro buses operated on a limited schedule, Maryland commuter bus service was cancelled and VRE cut back service, too.

Air travel also was disrupted. But the two Washington airports that were closed early today -- Dulles and Reagan National -- have reopened. Delays can be expected this afternoon, however. Flights heading into Dulles International Airport were running two hours late, on average, at mid-afternoon.

In hard-hit Prince George's, County Executive Jack B. Johnson (D) held an afternoon news conference to assure residents that roads were being cleared and that he would stay on power companies to quickly restore electricity to the thousands of residents who had lost it.

Across the Washington region, frozen pellets rained down steadily before dawn, pinging noisily off buildings and roadways and leaving cars, streets and walkways encased in a thick layer of snow and granular ice.

Nearly 125,000 homes and businesses lost power{vbar}, the vast majority of them in Prince George's and Anne Arundel counties.

Although precipitation tapered off in most areas by 9 a.m., and plows were clearing main roads, conditions remained treacherous in many neighborhoods, and motorists were advised to either stay home or drive extremely carefully. Cars needed to warm up for 10 minutes or so before ice could be scraped off the windshields.

With the federal government electing to open late -- and many private businesses also allowing employees a liberal starting time -- the morning commute was slippery and drawn out. Although roads continued to improve over the course of the day, traffic officials warned drivers to remain vigilant and use caution especially in areas that could freeze up again, such as overpasses.

Temperatures had climbed above freezing by early afternoon{vbar}, and forecasters said they would hover in the low- to mid-30s through the afternoon, with winds picking up and snow flurries possible. Overnight lows will drop to 15 degrees, with a high of about 26 degrees expected tomorrow.

Accumulations of snow and ice ranged from about two inches in and near the District to up to five inches in some outlying areas.

The good news? Most of what fell was sleet, or tiny ice pellets. The much-predicted, and dreaded, freezing rain was limited, for the most part, to Anne Arundel County and the part of Prince George's County that lies east and south of the Capital Beltway.

Sleet covers roads and walkways with a grainy layer that provides at least some traction, while freezing rain solidifies on contact with power lines, tree limbs and asphalt, leaving glossy sheaths of ice that can down power lines and render roads impossible to navigate.

National Weather Service meteorologist Brandon Peloquin said freezing rain falls when the air temperature hundreds or thousands of feet above ground is warmer than 32 degrees. If temperatures up there are hovering around the freezing mark, the precipitation turns to sleet. If it is well below freezing, snow falls.

"In terms of wintry precipitation types, freezing rain is worse and more dangerous than sleet," Peloquin said. Freezing rain "turns into a glaze of ice that turns the road into a skating rink, basically."

Utility companies -- which had braced for massive power outages if the storm had involved more freezing rain -- said damage was significant, but not overwhelming. Prince George's and Anne Arundel were hardest hit, especially the areas around Bowie, Clinton and Annapolis.

As of 5 p.m., Pepco{vbar} was reporting nearly 25,000 customers without power, almost all of them in Prince George's; Baltimore Gas and Electric{vbar} said more than 67,000 homes and businesses were without power in Anne Arundel, along with about 17,000 customers it serves in Prince George's and 2,900 in Calvert. Dominion Power{vbar} had about 4,900 customers without power in Northern Virginia--down from 12,000 this morning.

The Southern Maryland Electric Cooperative{vbar} , which supplies power to Charles and St. Mary's counties and portions of Calvert and Prince George's, reported more than 8,000 homes and businesses affected by the storm.

In Prince George's County, Johnson had tough talk for Pepco and BGE. He said the last time the county faced widespread outages, the power companies had promised they were making improvements to quicken their ability to respond. "We're expecting a better response than we had last time," he said.

Standing at the county's central snow command, in front of a bank of monitors displaying video from several county intersections, Johnson also had promised that neighborhood roads that were not blocked by trees would get a pass by a snow plow by 10 p.m. last night.

He said residents whose streets were not cleared by that time should report the problem at 301-350-0500.

Prince George's officials said 12 crews were working to clear what they estimated were dozens and perhaps hundreds of fallen tree limbs that had fallen on county roads. The problem was countywide, they said, but especially pronounced in the county's rural southern end.

In the Disrict, some commuters who did venture into work today observed that certain main arteries into the city hadn't been cleared.

When asked about those concerns, the Fenty administration said they effectively executed their snow plan.

"Our job is to make sure the streets are safe and passable, and I think we've achieved that quite well," said Emeke Moneme, acting director of the D.C. Department of Transportation, at a news briefing in the morning.

Moneme said that the evolving nature of the storm forced his team to make certain tactical changes such as when to put down plows and temporarily stop salting streets.

Asked later in the day to grade his administration's performance, Mayor Adrian M. Fenty declined to give a specific answer.

Virtually all major public school systems, as well as private schools, were closed for the day, extending a winter weather hiatus that began yesterday in many juridictions{vbar} with early dismissals.

One exception was St. Mary's County Schools in Southern Maryland, where precipitation totals were lower. Schools there were scheduled to open two hours late. A complete list of closings{vbar} is available on{vbar}

Traction on the region's interstates and high-volume roads had improved significantly by 7 a.m., as increases in traffic helped disperse salt laid by transportation crews. "Most of the interstates are just wet pavement right now," said David Buck, spokesman for Maryland State Highway Administration.

In Montgomery County, Interstate 270 was reported running well, and few serious collisions had been reported--perhaps because few people were on the roads. But many side streets remained treacherous.

"There's no reason for anyone to be out there if they don't need to," said Lt. Eric Burnett, a police spokesman. "We have reports of numerous cars stuck."

In East Bethesda, where neighborhood streets are cleared by 8 a.m. in most snow storms, many streets hadn't seen a plow by noon. One plow driver, who wouldn't give his name, said the work was taking 50 percent longer than usual because the ice was much heavier to move than a more powdery snow. "The sleet makes it heavier and harder," he said.

In Prince George's and Anne Arundel, heavy ice and strong winds downed several large trees that blocked roadways, closing sections of Route 424 and Route 450. Most of the areas major highways remained more or less clear after fleets of trucks salted hundreds of miles of roadway in advance of the storm. Still, David Buck, a spokesman for the Maryland State Highway Administration, urged drivers to be cautious, especially as the day wears on and dropping temperatures cause roads to become icy and slick.

"It's going to take some time for the salt to take effect," Buck said. "We don't want people to get complacent just because the Beltway and the major highways are okay. This is not over by a long shot." He encouraged drivers to check road conditions at{vbar} before venturing out, and to exercise special caution when exiting interstates, as pavement temperatures on bridges and off-ramps are lower than those on the roads.

Virginia transportation department spokeswoman Joan Morris said the agency had deployed nearly 1,000 trucks to salt and treat roadways, but that they had yet to reach secondary routes and subdivisions. "It's still pretty treacherous out there," she said. "The challenge is that if you're in a subdivision, getting to the major routes will be a struggle."

Morris urged motorists to be patient while the agency worked to salt and plow roadways. "Folks need to understand that we had sleet and ice all night long," she said. "We've got a long, hard day ahead of us. That's why we're hoping people will stay home and give us time."

The sight of piled-up slush between lanes and on highway shoulders should signal drivers to slow down, Morris said. "Our goal is to treat all high-volume roads within 12 hours of the storm ending," she said. "For residential streets, our goal is to get them sanded and plowed up to 18 hours after the storm ends. Based on the forecast we have today, it could be tomorrow morning before we have gotten to every last subdivision."

In the District, crews were working to plow and salt major arterial routes, said D.C. Department of Transportation director Emeka Moneme. Many downtown streets were clogged with slush. "Things are slick," Moneme said. "We had a lot of precipitation early this morning. We're encouraging people to leave early and take their time."

The city removed some trucks from the streets during the morning rush to help with traffic flow, but around 10 a.m. the full compliment of trucks got back on the streets. Moneme said crews would remain at full deployment through the afternoon. "The key is to get all the muck out and retreat the streets before temperatures plunge," said Erik Linden, a transportation department spokesman.

Officials were monitoring operations from the department's Traffic Management Center, where a wall of television screens project images of key intersections in the city. One problem area was on Interstate 295 near the Blue Plains Treatment Plant, where a northbound lane remained icy and the television monitor showed cars skidding. A crew was deployed to clear the location. Another spot of concern was on 16th Street NW, a major commuting thoroughfare that--according to the monitors--was covered with snow and ice on the road, significantly slowing down traffic.

District officials said a map posted on the city's website{vbar} can be used to show residents which roads have been treated and what treatments have been applied.

The ice and snow froze much of the region's air traffic.

Reagan National Airport shut down flights around midnight, but reopened at 10:40 a.m. Officials said flights were badly backed up, and delays and cancellations were expected to continue throughout the day, in part because of weather problems elsewhere in the country.

Dulles International Airport closed at 5 a.m., and opened one runway for departing and arriving aircraft shortly after noon. By 5 p.m., all three runways were open. Earlier, workers at Dulles passed out 250 blankets to stranded travelers who were sleeping on the floors.

Baltimore-Washington International Thurgood Marshall Airport is open, spokesman Jonathan Dean said, and all runways are operating, but there are significant delays and cancellations there as well. People planning to fly out of the Washington area today should check with their airlines to see if flights are cancelled, officials said.

Metrorail extended its rush hour schedule to about 10:30 a.m. because of the federal government's delayed opening, spokesman Steven Taubenkibel said. On the Red Line, trains were delayed traveling north to Shady Grove because of sparks reported about 8:30 a.m. from an insulator on the tracks underneath the electrified third rail between the Dupont Circle and Woodley Park stations.

Fire and Metro personnel were in the process of clearing up the incident, but delays are expected to last until about 9:30 a.m. because of that incident and a separate mechanical problem on another Red Line train at Van Ness headed toward Shady Grove, officials said.

MetroAccess, the service for the elderly and disabled, is operating but officials are asking that passengers with non-emergency trips reschedule to another day.

Metrobuses were running only on main arteries, because none of the side streets were deemed passable, Taubenkibel said. Even on the main roads, buses were experiencing major delays, Taubenkibel said.

Early this morning, the District's Downtown Circulator bus shut down service into Georgetown and was running 45 minutes to one hour late, officials said. By mid-morning, the Georgetown service had resumed.

According to the Maryland Transit Administration Web site, all commuter bus service in Maryland was cancelled for today.

Snow and ice also were causing significant delays on all three MARC lines, according to the system's Web site{vbar} In a posting on its Web site, MARC said conditions in parking lots and on platforms were poor and urged riders to take extra caution in driving and walking this morning. When boarding or detraining passengers should hold on to the handrails, the Web site said, because floors in railcars can become slippery from melted snow.

Staff writers Theresa Vargas, Rosalind S. Helderman, Raymond McCaffrey, Nick Miroff, Dan Morse, Candace Rondeaux, Elissa Silverman, Miranda S. Spivack, Lena H. Sun and Steve Vogel contributed to this report.