The Potomac River and other Washington area streams, swollen by heavy rains and melting snow. spilled over their banks in places yesterday, producing scattered flooding, but forecasters said the waters should start receding this morning.

The Potomac River reached a record February flow rate of 127 billion gallons a day at Little Falls late yesterday, sending the water over the banks for first time in more than two years. Low-lying spots along the Georgetown waterfront and on Ohio Drive SW were swamped with water. Boat houses near Key Bridge were flooded.

Upstream, the river spilled over into the C&O Canal at Lock Six and Lock Seven near Glen Echo, surrounding at least one of the lock houses.

Other area streams, notably the Patuxent and Monocacy rivers in suburban Maryland, also went over their banks in places, but did little damage. The Patuxent flooded low-lying parts of Laurel Sunday, forcing the evacuation of 360 people from an apartment complex. Most returned late yesterday.

The heavy rains -- more than three inches since last Friday -- combined with melting snows from last week's near-record snowstorm to beset the area with problems yet another day.

Morning rush hour was a nightmare again for many commuters with cars and buses slowed often to a stand-still by flooded roads, detours, potholes and lingering patches of snow. Some inbound buses from Virginia were an hour or more late reaching downtown, a Metrobus spokeswoman said.

In the evening rush hour, traffic also was plagued -- this time by the mass malfunction of traffic lights at some 30 intersections downtown. Police officers were dispatched to some of the intersections to help move traffic.

Huge tieups occurred as the traffic lights -- all stuck on either red or green -- remained out of order from about 3:45 p.m. to 6:30 p.m., and weary, impatient commuters clogged the intersections.

Traffic officials said the affected area was bounded roughly by M, E, 12th and 16th streets NW. D.C. Transportation Department night supervisor William Long said temporary repairs were made by 6:30 p.m. to permit the lights to change, although not on the special sequence for rush hour traffic. Permanent repairs will be made today, he said.

Long said the malfunction apparently was caused by water seeping into the system and causing a short circuit.

In the suburbs, police closed many roads because of local flooding. Loudoun County was placed on "emergency condition" by its civil defense office and its public school system was closed for the day.

Portions of 28 roads in Loudoun County were closed because of flooding. Fairfax County closed 26 roads and Montgomery and Prince George's counties closed at least 20 between them.

Flooding in the area was expected to subside today, and the National Weather Service said sunshine should be on the way tomorrow. Thursday should also be fair, but some preciptiation may return by Friday or Saturday, forecasters said.

The U.S. Gelogical Survey clocked the Potomac River at Little Falls late yesterday at a rate of 127 billion gallons a day -- the highest rate for any day in February since the survey started keeping records in 1930 and the greatest single flow rate since Oct. 11, 1976, when the river was clocked at 134 billion gallons a day.

The flow leaped more than 20-fold since last Friday when the river was measured at about 5 billion gallons a day -- only slightly more than half the normal flow rate of 9 billion gallons a day at this time of year.

The river had fallen to a low level recently because of little precipitation other than the recent heavy snows which clung to the ground and did not begin to augment the river flow until large-scale melting commenced last Friday with the area's warming trend and accompanying rainfall.

The D.C. Transportation Department, under orders from Mayor Marion Barry, began a crash program Sunday to plug up the thousands of potholes slowing traffic and damaging autos on Washington streets.

Working round the clock, 29 special road crews filled in potholes with temporary patches on some of the hardest hit roadways -- the Whitehurst Freeway NW, New York Avenue NE, the Benning Road NE viaduct and Interstate Rte. 295 -- "and we've made some pretty good progress," said transporation department spokesman Gary Wendt.