Scores of highway work crews began spreading chemicals and sand on roads around the Washington area late last night and early today in the opening battle against what appeared increasingly to be a major and potentially paralyzing winter storm.

As the heart of the massive storm system churned slowly out of the south, state highway officials in western Fairfax County sent out more than five dozen trucks to spread chemicals in their area, where about two inches of snow had accumulated by 1 a.m.

Although some predictions of heavy snow here earlier this winter proved to be exaggerated, the National Weather Service warned this morning that the storm could bring the area's heaviest snowfall since the Washington's Birthday blizzard of 1979.

Calling the storm "potentially dangerous," particularly to those who might be stranded, forecaster Gary Ellrod said he expected snow accumulations of two to four inches in most parts of the area by daybreak and up to a foot by evening.

High winds are expected to blow the snow into drifts, while authorities predicted that below-freezing temperatures through Saturday would slow melting and impair removal efforts.

The storm, which has been surging slowly but inexorably toward the area for the last two days, made its formal arrival here at 9:15 p.m. when the first flakes fell at National Airport.

With midnight approaching, snow beginning to stick to the ground and a private consultant predicting as much as five inches by morning, the District called for "full mobilization" of its snow removal forces. Truck drivers were called in from home and by 1 a.m. 56 vehicles were spreading salt and sand.

In Prince George's County, where snow began falling heavily early today, and some above-average accumulations were expected, the county's snow removal chief was among the most wary of the possible impact of the storm.

"I'd say rush hour could be a bear . . . ," said Vaughn Barkdoll, director of public works. He cited private forecasts suggesting snow might fall this morning at the rate of one inch an hour, which would overwhelm snow clearing efforts and "could be pretty dangerous."

Snow clearance officials around the area said they planned to rely on spreading salt and sand as their first line of defense, then begin plowing if and when accumulations reached three or four inches. Still, in the words of Art Peyton, Alexandria's street maintenance superintendent, with heavy snows not expected to arrive until morning, the situation appeared "touch and go."

By early today, nine inches of snow had blanketed Roanoke, Va. Forecasters said the storm was being fed by two weather systems--one, centered in the south, was supplying huge amounts of moisture from the Gulf Stream, while the second, centered in the Arctic, was providing vast quantities of cold air.

Those who become stranded, said forecaster Ellrod, face "the possibility of life-threatening" conditions.

Even so, some Washingtonians who recalled the blizzards predicted in January that turned out to be only flurries appeared unmoved by the crisis tone of the current forecasts.

Paul Meagher, honorary "corporate weatherman" for the Hawk and Dove bar on Capitol Hill, said late yesterday afternoon: "I just stuck my finger out the door. I'm predicting a real scare, a tremendous scare.

"The scare is real, but the snow won't be, " he said. "I'm predicting about four inches. But people will still call in sick--they won't go to work Friday.

"We need a scare," he said. "This is hibernation week, after January, which was a misplaced November with five football games, four of them at home. There's really a psychological need for winter."

Nell Bowers, an administrative assistant at D.C. General Hospital, said she would not leave home if the snow materializes and offered this suggestion for the government and every other employer: "I think everything should close down for the day and leave the snow undisturbed. Only photographers and TV camera persons should be allowed to work so they can take pictures of all the beautiful sights."

While some contemplated a snowbound day, others flocked to grocery stores to stock up. "Everytime it snows this happens," Fred Bladen, the relief manager at a Safeway in McLean, said as he surveyed his packed store.