Washington's third winter storm in eight days caused a flurry of minor traffic accidents during yesterday evening's rush hour, forced numerous motorists to abandon stalled cars, and cast a cold, wet blanket on Valentine's Day observances.

However, after predictions throughout the day of as much as three to five inches of snow sent alarmed area residents to stores to stock up on staples, the National Weather Service said late last night that it no longer expected more than one to two inches.

Snow was falling briskly in the city about 10 p.m. in what forecasters said would be the last hurrah for the storm that had swept east from the Tennessee Valley during the day and early evening.

With many area residents trying to avoid snow-spawned tieups and get an early start on the long Washington's Birthday holiday weekend, the area had two rush hours yesterday. One started as early as 3 p.m., and the other at the usual 5 p.m. Both produced numerous minor accidents as streets rapidly grew slick and slushy.

In perhaps the most serious accident of the day, one person was severely injured about 7:30 p.m. in a chain-reaction pileup of at least 10 cars on a snow-slick stretch of Richmond Highway in the Lorton area of Fairfax County, authorities reported.

Elsewhere in the county, police reported that collisions of the fender-bender variety occurred by the dozens. Cars slid from roadways in the Burke area. Part of Rte. 1 in the southern part of the county near Fort Belvoir came to a standstill for an hour.

"Traffic is a mess," a spokesman for the Maryland State Police in Rockville said about 5:30 p.m. "We've had a bunch of small accidents and they're the ones that are backing us up. Traffic is about at a crawl."

Although no more than half an inch or so of snow had been reported by late afternoon, it was enough to cover sidewalks and streets with slippery slush. In the downtown area, particularly near the 17th Street and Connecticut Avenue NW corridors, traffic appeared for a time to approach gridlock.

Cars and buses clogged the streets. Horns honked with irritated urgency. The sirens of stalled emergency vehicles echoed off the concrete walls of office buildings.

About 4:30 p.m., near the start of the day's "second" rush hour, "it really started to go bananas," said Doug Neilson of the Potomac Chapter of the American Automobile Association, as AAA members began telephoning for assistance.

At Dulles International Airport, a PanAm Boeing 747 slid from a taxiway about 5:30 p.m. after arriving from London, and one of the jetliner's wheels became stuck in the mud, airport authorities said. Passengers were removed and taken to the terminal in mobile lounges.

National Airport closed at 8 p.m. for about 45 minutes so that an accumulation of about half an inch of wet snow could be removed from runways. The closure, and a period of low visibility for planes landing from the north, forced diversion of some flights to Dulles, a Federal Aviation Administration official said.

At Dulles, where airport officials reported about an inch of snow, individual runways were shut down for plowing for as long as 40 minutes, but the airport never closed.

Throughout the area, highway department crews spread sand and salt, their efforts sometimes impeded by the crush of traffic.

In the District, about 200 workers using 81 trucks and a variety of other vehicles went into action about 3 p.m., shortly after the first fine flurries began dampening city streets.

By dusk, most of the city's main arteries had been treated at least once, and crews were beginning to make the rounds again, said George Schoene, chief of the bureau of traffic services in the department of public works. At that point, he said, major roads in the District appeared to be in good shape.

Late last night, Virginia State Police in Fairfax County described roads there as "mostly wet," and "not in too bad shape."

Throughout the area, highway officials, as well as apprehensive citizens, appeared relieved by the new Weather Service forecast issued about 9 p.m., which called for accumulations here of one to two inches instead of the three to five inches predicted earlier.

Forecaster Larry Wenzel said it had appeared earlier that a low pressure system in the Tennessee Valley bringing the snow would churn northeastward. But it turned out that the storm center headed farther to the south before moving out to sea.

The rosier outlook could not completely replace the wilted bloom of Valentine's Day. At least three local restaurants reported several cancellations each for Valentine's Day dinner.

"We had about eight people cancel, and they said it was because of the weather," said Berkley Stephens, maitre d' at the Marco Polo in Vienna, when the snow was at its peak.

At Vermont Avenue and L Streets NW, a flower vendor who had stocked up on red roses cast a cold eye on the falling snow.

"This is very bad weather for my business," he said. "This is my big business day of the year and everyone is leaving early because of the snow."