Washingtonians who suffered through the last three days of flooded basements, overflowing creeks and ceaseless downpours - including a record 2.81 inches of rain on Sunday alone - should rejoice. Even if the area should get a heavy snowfall tonight, as forecasters have tentatively predicted.

This is just natures's way of making up for last summer's drought.

With more than 4 inches of rain accumulated so far in December at the National Weather Service measuring station at National Airport, the year's total now stands at about 35.35 only 3 1/2 inches shy of the annual norm of 38.89 inches.

More than 14 of those 35.35 inches have fallen in the last 11 weeks, compensating for the disturbing dryness of the first nine months of the year.

In the first six months, barely 12 inches of precipitation fell, compared to a normal accumulation of 18.42 inches.

It was not until October that substantial soaking rains finally began to replenish the dwindling Potomac River and Occoquan Reservoir, the two principal sources of drinking water for the area. Rains totaling 5.35 inches in October and 4.81 inches in November also began to recharge the area's depleted water table.

The storm system that brought the Washington area's downpours of the last three days is moving slowly eastward into the Atlantic. but some lingering showers are expected here today, possibly turning to heavy snow tonight before tapering off Wednesday.

The rains of Saturday and Sunday caused minor flooding and disrupted traffic in parts of the area. Many home owners reported flooded basements.

Leo Harrison, river forecaster for the weather service, said most flooding has abated by yesterday with only minor problems remaining on some roads in southern Prince George's County.

"Everything else seems to be under control," Harrison said.

The U.S. Geological Survey yesterday day reported the Potomac River flowing at a rate of 24.7 billion gallons a day at Little Falls, about five time the average daily rate for the month of December. Though well above normal, the river has caused no flooding and its flow rate is well below record levels.

Geological Survey spokesman Frank Forrester said rains in the last 11 weeks also have helped to recharge the area water table. Ground water in a sample well near Colesville, he said is nearing its normal level of 12.6 feet below the surface of the ground. Another well near Fairfax City is still two feet below normal, he said, and is not expected to rcach normal even by the end of the year.

The storm system that hit the Washington area also battered much of the Delmarva Peninsula yesterday Ocean City, Md., Mayor Harry Kelly reported that surf had covered the entire beach at that resort center and waves were occasionally breaking over the broadwalk.

"You get a gut feeling about these things," he said, "and this one ain't good."

After another storm last Oct. 14, Ocean City spent $150,000 installing barriers to prevent beach erosion a percennial problem on the Maryland coast.

Just Friday we had the beach in good shape," said Kelly yesterday, and now it's gone, $150,000 down the drain."

He said water had sceped into several streets from high waves, "and there probably will be some property damage - what and how much we can't tell till this storm's over."

In the Washington area, total precipitation for December so far stands at slightly more than 4 inches, already well above the normal of 3.04 inches for the entire month.

Of the total so far, 2.81 inches fell on Sunday alone, a record accumulation for a 24-hour period in December. The previous record was 2.57 inches set 76 years ago.