Though the first significant snowfall is not expected until Christmas, if then, Washington area officials have known for months how they will launch their assaults on the fluffy white flakes that look so pretty until one has to drive through them.

"We're ready," said Robert Mangum, chief of Montgomery County's operations division, where 181 pieces of equipment and 345 employes will be mobilized to clear 1,755 miles of roads and handle other weather-related emergencies.

They are "on alert" in Northern Virginia, too, said Linda South, spokeswoman for the Virginia highway department. The agency has stockpiled 18,900 tons of sand, 12,000 tons of salt and 754 tons of calcium chloride for use in Fairfax, Loudoun and Prince William counties, where more than 600 pieces of equipment are primed to tackle about 4,000 miles of roads.

Working from "snow books" -- detailed manuals on what gets done when -- and operating out of headquarters dubbed "snow rooms" by some jurisdictions, local governments have developed plans of attack with all the precision of a military combat mission.

Most local officials even subscribe to private forecasting services that provide specific weather information and enough advance warning that officials hope will let them know when to call out the crews and when it is safe to keep them home.

In Montgomery, major arteries such as Democracy Boulevard, Montrose Road and Randolph Road get cleared first, then secondary roads, followed by parking lots for county employes. The Maryland State Highway Administration clears all interstate thoroughfares, relieving the county and other state localities of that responsibility. Montgomery's hospitals and schools make their own arrangements for snow removal.

To survive an anticipated hard winter, Prince George's County has stocked 17,000 tons of salt, according to Sylvester Helminiak, its associate director for highway maintenance. About 90 snowplows, including 20 privately owned trucks that will be rented and fitted with plows, are set to roll along 48 routes, each with its own list of street-plowing priorities.

There is good reason for all this preparation.

Gordon Barnes of WDVM-TV (Channel 9), the area's preeminent media weather forecaster, told viewers last month to expect below-normal temperatures and above-normal snowfall this winter. Normal snowfall is about 28 inches.

Barnes, whose specialty is long-range forecasting, said the region likely will get four to six snowstorms, with Feb. 7-10, Feb. 24-27 and March 8-11 the most likely dates for heavy snow. It could rain or snow Dec. 24-26 and Jan. 28-30, according to Barnes, who is predicting three inches or more of snow with each storm.

One-half inch of snow, he noted wryly, is enough to put the Washington area in a panic.

But the region has seen worse. There was the February weekend snowstorm of '79 and the February blizzard of '83, which struck on a Friday and forced thousands of motorists to abandon their cars. And there was last December's bitter ice storm.

In D.C., officials have been meeting monthly since August, updating the "snow book," testing equipment and making sure all systems were "go" by Nov. 15, when the snow watch officially began.

The D.C. Department of Public Works has 200 plows, salt spreaders, road graders, sand loaders and other equipment, and, like other jurisdictions, it has contracted with private owners for 179 vehicles for "standby readiness."

Ann Hoey, the department's administrator of public space maintenance, said preparing for snow means arranging for plows, salt spreaders, dump trucks and staff vehicles with four-wheel drive. It means pinpointing gasoline and diesel fuel availability, coordinating the radio frequency for mobile units, and training drivers. It means setting out 200 barrels of sand that motorists can use to help with slippery spots on the city's steepest hills.

Hoey said it even means "establishing who wakes who in the middle of the night."

The District has 1,100 miles of streets, and the snow plan spells out which ones are plowed first -- the bridges leading in and out of the city. The bridges are part of 180 miles of snow emergency routes, "with the signs that everybody sees and nobody thinks about" when the time comes, said a department spokeswoman.

Bus routes get special attention. The jurisdictions work with and loan equipment to the Washington Metropolitan Area Transit Authority to help keep bus routes and sidewalks around Metrorail clear. Federal agencies are responsible for plowing on federal land.

In Northern Virginia, Alexandria, Falls Church, Fairfax City and Arlington County handle their own snow-removal chores. Arlington has 50 snowplow trucks and about 100 employes, and it dispatches both to various zones in the county where they clear the major roads and bus routes first.

To protect these priorities and because the use of county equipment "is a sensitive subject with us," according to Dennis Johnson, chief of operations for Arlington's Public Works Department, a private contractor has been hired to plow the snow around county government facilities, starting with police and courthouse parking lots.

Alexandria has 11 city trucks and a road grader and rents six pieces of equipment to supplement snow removal work. More than 60 employes, working in 12-hour shifts, are assigned to snow emergency tasks, and the city draws on additional employes as needed.

From October through February, a night crew is kept ready "in case they tell us it will snow at midnight and it suddenly shows up at 9 p.m.," said Richard Pelky, deputy director of Alexandria's Department of Transportation and Environmental Services.

Such awkward surprises occur rarely, according to local government officials, who credit their private forecasters with giving them a jump on weather conditions.

"Our forecasts are tailored to the jurisdiction and to how the atmosphere interacts with the terrain," said Joel N. Myers, a meteorologist and president of Accu-Weather, the forecasting firm used by most Washington area localities.

The firm, based in State College, Pa., relies on what Myers said are "millions of bits" of weather data that can help tiny Alexandria or huge Montgomery County prepare for snow or ice and assign equipment accordingly.

The information, for which Fairfax County, for instance, pays about $800 a year, can be very detailed. Montgomery County can learn, for example, that it will snow in its northwest sector, with its higher elevation, while the southeast portion of the county can expect slush.

"The radio may say 'snow tonight,' but if the client knows it won't be until 11 p.m., the crews can stay home until then," said Myers. "If it's going to be too wet to accumulate, you may not need crews at all, and if it's going to be snow turning to freezing rain, you'll need [only] salt and sand."

Fairfax County, despite its size and vast network of roads, is directly responsible for only about seven miles of street clearing. The rest, as with all but two Virginia counties, Henrico and Arlington, is left to the state highway department. This frees Fairfax's 18 trucks for snow emergency assistance to police, fire and rescue services as well as to county employe parking lots.

Despite suspicions to the contrary, District and other local government agencies said they do not clear streets based on where their respective VIPs live. They will sometimes use four-wheel drive vehicles to get officials in and out of their homes, but traffic volume is supposed to be the immediate criterion for street clearing.

"The mayor's Marion Barry on Suitland Road, and if Pennsylvania Avenue is not cleared, he still wouldn't be able to get out," said Hoey. "You've got to get the main roads before the side streets."