Heavy rains yesterday raised the level of the Potomac River to near-normal and promised some relief for the three-fourths empty Occoquan Reservoir in Northern Virginia.

The storm system brought gale-force winds and some flooding to parts of coastal Virginia, Maryland and Delaware and even dumped up to four inches of snow on Southwestern Virginia. It had left almost three-quarters of an inch of rain at Washington National Airport by early last night.

A spokesman for the Fairfax County Water Authority said the authority expected about a half inch of rainfall throughout the 557-square mile Occoquan River watershed.

This should provide 100 to 150 millions gallons of runoff into the reservoir, which means an additional three or four days supply of water for suburban Virginia users, according to water authority spokesman James A. Warfield Jr.

Equally important, he said, the soaking effect of yesterday's rain will help to increase runoff in future rains.

Yesterday's precipitation, like that of last weekend, should also delay the authority's decision to start buying water from the city of Manassas to supplement the badly depleted reservoir. Under authority guidelines, it would start buying water when the reservoir falls to 94 1/2 feet above sea level. Warfield said the reservoir stood at 96 feet late yesterday.

The condition of the Potomac River, which provides the primary water supply for the District of Columbia and suburban Maryland was more encouraging. The U.S. Geological Survey reported the river flowing at the rate of 1.7 billion gallons a day at Little Falls, which near the normal level of 1.8 billion gallons a day for October. This well above the daily amount of about 276 million gallons drewn from the river by the District and suburban Maryland.

The river's current flow is also about 30 per cent higher than it was during September when it averaged barely one billion gallons a day - the lowest September level since records were started in 1931.

Elsewhere in the region, Virginia recorded its first snowfall of the season starting Thursday and continuing yesterday. By last night, four inches had been reported in parts of Floyd and Patrick Counties in the mountainous southwest.

The National Park Service said portions of the Blue Ridge Parkway were closed because of slush and ice on road surfaces.

No deaths or injuries were reported as the storm system moved slowly eastward over the Atlantic Ocean. Torrential rains and winds up to 43 knots caused local flooding in coastal areas, however, and the Coast Guard rescued a Maryland man, his wife and their three children marooned on Cedar Island on the Virginia Eastern Shore.

Forecasters called for clearing weather in the Washington area during the night with sunny skies and temperatures in the mid-60s today.