The Washington area took an early slide today as the federal government, local businesses and many schools systems closed in the afternoon to avoid dangerous travel conditions that officials said are likely to materialize as temperatures drop and the mix of snow and rain that began this morning turns to ice.

Officials reported a busy early rush hour after the Office of Personnel Management announced federal offices were closing at 2 p.m. And police and traffic services reported a number of accidents from the slippery roads, but most were minor--at least so far.

The danger will increase, public works officials and forecasters said, as the mercury -- and the asphalt temperature -- drops. By 4 p.m., the temperature in the District had fallen to 28 degrees, according to the National Weather Service.

Weather Service forecasters said they expected accumulation of one to two inches of snow today, followed by a change over to a "significant freezing rain" that was predicted to begin about 5 p.m. and to sheath the area in one-quarter- to one-half-inch of ice -- possibly leading to extensive power outages and dangerously slippery roads.

Winds were also expected to pick up to 10 to 15 mph tonight, presenting another hazard that could affect power outages.

Temperatures were likely to fall as low as 20 degrees on Wednesday, with additional snow possible in the afternoon.

Virginia Gov. Timothy M. Kaine declared a statewide emergency this afternoon so that state agencies could begin to take action if needed for the storm damage expected in Northern Virginia and the Shenandoah Valley. The Virginia National Guard will deploy about 150 troops and equipment to help if needed.

"This disaster declaration allows us to pre-position certain assets in specific regions where weather could create problems," Kaine said.

Airlines reported cancellations at local airports, some of which were caused by weather problems in other cities that delayed or stranded aircraft. United shut down all traffic into the three airports serving Washington and Baltimore; Southwest and US Air reported a large number of flights were cancelled. Travelers were advised to check with their airlines before heading to the airports.

Susan Bryant, an OPM spokesman, said the government shut down early because weather reports indicated that road conditions could worsen in late afternoon.

"We want to get people off the roads before dark," she said. Emergency personnel will still be required to report to work.

The federal government's last-minute decision to close early meant that Metro was scrambling in the early afternoon to get enough trains and operators to the busy downtown stations and bracing for jammed platforms and trains, officials said.

Metro was notified by OPM officials at 1:05 p.m. that the federal government was closing early, according to Metro spokeswoman Lisa Farbstein. Typically, the rail system needs two to three hours of notice for major shifts, such as a change in rush hour, because train operators need to be called back to work and rail cars need to be moved from rail yards to downtown stations.

For a typical rush hour, Metro uses 123 train operators and 758 rail cars, with trains ranging from four to eight cars. Because of today's short notice, Metro was forced to use more eight-car trains, according to Steve Feil, Metro's chief operating officer for rail.

During a typical weekday rush hour, which starts at 3 p.m., between 40 to 45 percent of the riders are federal workers, officials said. In addition, in bad weather many private-sector businesses follow the federal government's lead, putting addition commuters on the rail.

"We're disappointed we didn't have more advance notice," said Metro spokeswoman Farbstein. "We would have had a higher level of service out there."

Maryland, Virginia and District officials reported heavy traffic congestion by 3 p.m., but no major incidents.

"It's heavier at 2:10 but it'll be lighter at 5:10," said Maryland State Highway Administration spokesman David Buck.

Buck said pavement temps were still above freezing, and that crews would be re-applying salt over the next few hours.

Maryland had 1,300 trucks out treating roads, while 739 were working in Northern Virginia.

Erik Linden, a spokesman for the District's Department of Transportation, said the agency was fully deployed with 150 trucks on roadways and crews working 12-hour shifts with heavy plows and light plows.

"Right now it's a road treatment operation," he said. "We're not seeing anything out of the ordinary."

But police cautioned that could change quickly.

"We're starting to hear about roads icing over," Lt. Eric Burnett, a spokesman for Montgomery County police said at 3:15. "Up to now, it's been uneventful, but it's going to be a busy night."

"It's getting ugly out there," Burnett added.

Montgomery declared a snow emergency at 4 p.m. That prohibits parking on snow emergency routes and requires motorists to have snow tires on their vehicles.

Anne Arundel police reported about 50 accidents yesterday by mid-afternoon, said Lt. David Waltemeyer, a police spokesman. No serious injuries were reported.

"It's about double what we normal had, so weather certainly had an effect," Waltemeyer said.

On the heels of the federal government closure, the Montgomery County government declared a liberal leave policy for employees to be in effect immediately. Most non-essential employees may use unscheduled annual leave, paid time off, leave without pay or compensatory time today without prior supervisory approval.

All county facilities, including libraries, recreation centers and health clinics will close today at 5 p.m. All county programs and activities are cancelled for the remainder of the day.

Officials warned that passengers of the county's Ride On bus service should expect delays and detours, although the system is to operate on a normal weekday schedule.

School systems including Fairfax, Montgomery, Prince George's, Anne Arundel, Loudoun, Arlington, Falls Church, Frederick, Charles and Calvert counties closed their doors at least two hours early today so that students and staff could get home before conditions worsened. Most school systems, including the District, cancelled evening programs.

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The only major Washington-area school system to shut down for the entire day was Prince William County, which joined more rural systems including Clarke, Culpeper, Fauquier, Stafford and Rappahannock in Virginia and Carroll and Washington counties in Maryland. Many private schools also closed.

Officials in Prince William said they based their decision on the forecast, rather than current road conditions. George Kisha, associate superintendent for finance and support services, said the system did not want students coming to classes only for them to go right back home when the roads -- especially in more rural and hilly areas -- would be at their most dangerous.

"If we're going to err, we want to err on the side of safety," Kisha said. "A few years ago we had icy conditions and things got terrible around mid-day and we had problems getting kids home."

Starting late Monday night, snow removal and utility line crews said they were on high alert. Freezing rain, which falls as liquid, turns to ice on contact with cold streets and sidewalks. The weight of clinging ice can break tree limbs and bring down power lines.

"We'd rather have 15 inches of snow than an inch of ice," said Bob Dobkin, a Pepco spokesman. "If it stays a quarter-inch, that wouldn't be too bad. If you get over a quarter-inch, it becomes problematic."

Both Dominion Virginia Power and Pepco urged customers to consult company Web sites, or, for advice. Pepco's customer care number is 202-833-7500. Dominion's customer service number is 888-667-3000.

Baltimore Gas and Electric Co., which serves some customers in Montgomery, Howard and Prince George's counties, was also extending shifts and closely monitoring the weather. "We are certainly prepared for whatever Mother Nature might bring," said spokeswoman Linda Foy. BGE's customer service number is 410-685-0123. Its Web site is

The Virginia Department of Emergency Management urged people to have extra food, water, batteries, blankets and medication on hand in case of power outages and warned about the improper use of portable generators and heaters.

But the slow start to the storm, and the above-freezing temperatures earlier today, created at least a temporary sense that the region might have been over-prepared. Mickey Costanzo, 42, left his home in Mechanicsville, Md., at 4 a.m. to allow himself plenty of extra time to traverse slow-slicked roads and get to his job in clearing sidewalks and a plaza outside the Arlington County courthouse complex.

The roads, however, were not a bit slick.

So he got to work plenty early, and had to wait a few hours before enough snow accumulated for him to shovel.

"Nothing yet," he said shortly after 8 a.m., as the flakes fell faster but the roads remained warm enough to melt it on contact. He was careful to clear away whatever white stuff did stick to the plaza he was patrolling. "I just wanted to give people some traction, so they don't fall," Costonazo said. "I don't know why these women wear these high-heeled shoes."

Metro reported several delays during this morning's rush hour, most due to a short circuit at the Washington Reagan National Airport station that may have resulted from water on the tracks. Trains in both directions had to share a single track for more than an hour. Service reportedly had returned to normal by shortly after 9:30 a.m.

On Monday, officials said the transit system was installing de-icing equipment on 20 trains in advance of the storm, adding protection to the undercarriage motors to prevent snow ingestion and short circuits. It also planned to use a special cable on the electrified third rail to keep it warm enough in critical areas to prevent snow and ice buildup.

Metrorail will operate on a normal weekday schedule, from 5 a.m. to midnight. Metrobus will also run on a normal weekday schedule but will operate as road conditions dictate.

Staff writers Tara Bahrampour, Stephen Barr, Michael Alison Chandler, Maria Glod, Megan Greenwell, Nelson Hernandez, Dan Morse, Michael Ruane, Ian Shapira and Elissa Silverman, Theresa Vargas, Lexie Verdon, Steve Vogel and Martin Weil contributed to this report.