The third snowstorm of 1980 moved into the Washington area yesterday, dusting the landscape by late afternoon and then sending the cars of more than 150 homeward-bound motorists sliding into accidents during the evening rush hour.

Though the National Weather Service had expected two to four inches of snow to accumulate by dawn today, by 11:30 last night the flurries had tapered off and forecasters said they expected "little or no" accumulation during the early morning hours.

The snow did little more than wet streets throughout the area for most of the afternoon yesterday, but then outlying roads, residential streets and some major highways turned treacherous at sundown as the temperature dipped below the freezing mark.

The slushy snow caused five accidents on one short stretch along Washington Boulevard, near Shirley Highway and the Pentagon in Arlington County. But the bulk of the snow-related accidents -- about 100 of them -- occurred in Fairfax County, which got about an inch of snow by late last night. Most of the rest of the area had less than an inch by that time, according to the National Weather Service.

"Every call I pick up seems to be an accident," a harried Arlington police dispatcher reported. "We haven't had any major accidents, but the surfaces are real slick and people are driving sort of nutso. They're behaving like typical Washingtonians."

A police dispatcher in the District of Columbia gave a similar explanation for the rash of accidents: "Wet and slick streets and Washington drivers panicking."

Highway departments throughout the city and suburbs deployed several hundred salt and sand trucks by mid-afternoon, trying to cover the major highways with the abrasives in time for the rush hour.

But Don Keight, Virginia's top highway official in Fairfax County, said that secondary roads in Fairfax would only be sanded, which does not melt snow like salt.

"You couldn't afford to salt everywhere," said Keith, explaining that salt costs $35 a ton and sand only about $3.50 a ton.

One Fairfax commuter route, Lewinsville Road in McLean, which passes over the Capital Beltway, was blocked when a gasoline tank truck smashed into the overpass guardrail and knocked out a 20-foot section. No one was injured.

Washington-area school officials, some of whom were criticized last week when suburban schools closed when about two inches of snow fell, said they would make no decisions on closing schools today until the usual spot road checks were made between 3 and 4 p.m.

The storm, centered last night 15 to 20 miles off the North Carolina coastline and heading northeasterly, dumped much heavier amounts of snow -- up to 8 inches -- on the Carolinas and southern Virginia, according to the Weather Service.

Some of the accumulated snow in the Washington area may melt today, as temperatures are expected to hover just above freezing, and possibly go as high as 38. There is a 20 percent chance of mixed ran and snow, the Weather Service said. Temperatures are expected to fall to the mid-teens in the suburbs tonight and to the low 20s in the city.