Washington's first substantial snowstorm of 1983 trailed off into flurries late last night after turning roads slick and treacherous and causing scores of minor traffic accidents.

As the storm moved out of the area, leaving behind snow accumulations ranging from two to five inches, highway and traffic officials said they expected main roads and streets to be clear by this morning's rush hour.

Although some hilly spots on District streets became temporarily impassable early last evening and a portion of New York Avenue NE was closed for a time, such problems were alleviated within a few hours, said Seward Cross, an official of the city's snow removal center.

While cautioning that the morning could still bring hazards if overnight temperatures fell far below freezing, he said he believed that "we're going to ease right on through this."

Suburban officials appeared similarly optimistic about principal arteries, on which no more than two inches of snow had accumulated, most of it between 5 p.m. and 7 p.m., the storm's period of greatest intensity. Crews would be working throughout the night to spread chemicals on major roads, but officials warned that untreated streets in residential subdivisions may remain slippery.

Most area school officials said they expected to wait until morning before deciding whether to delay or cancel classes.

Sweeping northward from the Carolinas, the snowstorm arrived in Washington with the dawn. For much of the day fine flakes sifted down, lining tree branches, accumulating on car tops and lawns and fields. The residual heat of recent warm days, stored in streets and sidewalks, melted much of the snow as it fell.

With the onset of dusk, however, temperatures declined somewhat, and as they did, the storm appeared to intensify, filling the skies with large, fast falling flakes.

After an afternoon in which at least as many people appeared to be playing touch football as trying out skis and sleds, snow began to leave a white sheen on wet pavements. Many roads became icy.

"Roads are getting extremely slick," said a Fairfax County police dispatcher shortly after 5 p.m. "We are having many accidents throughout the entire county at this point."

Although Arlington police said only a few accidents had been recorded there, an Alexandria police dispatcher told of a rash of after-5 p.m. collisions, reporting "fender-benders all over the place," but no serious injuries.

In Montgomery County, four separate accidents involving 13 vehicles shortly after 5 p.m. blocked storm-slick Rte. I-270 near Falls Road and hampered snow removal crews, authorities reported.

National Airport, where four inches of snow was reported, shut down for almost two hours for snow removal starting about 6:30 p.m. Dulles remained open all day.

Earlier, flights to New York from National had been delayed by 30 minutes to permit snow removal at New York airports.

A spokesman for the Metro subway system said a total of 15 train operators were placed on standby at three terminal points, ready to begin running trains during the night to keep the tracks clear for morning traffic. Walks were being shoveled and snow melters turned on to keep switches from freezing, according to spokesman Al Long.

Temperatures are expected to rise to 40 degrees today.

Washington Post staff writers Michel Marriott and Edward D. Sargent contributed to this story.