Winter continued to loosen its grip on the Washington area yesterday as snow melted from many car-jammed roadways, and new rain -- possibly heavy at times -- was due to drench the landscape today.

Despite the combination of melting snow and rain, National Weather Service forecasters said last night they do not expect flooding here, at least in the next day or two.

The weather service posted a flash flood warning yesterday morning for far western Maryland and parts of southwest Virginia. But, at the same time, the U.S. Geological Survey noted that the Potomac River at Washington, while rising slowly in the last day or two, is not only far from flood stage but well below even its normal flood level for this time of year.

Meanwhile, the Washington area continued to thaw out slowly from Monday's massive snowstorm. Partially plowed roads and patches of ice produced scattered traffic jams during yesterday morning's rush hour again, but the situation was not as severe as Thursday's mammoth tie-up.

Montgomery County Police reported backups on Rockville Pike and Georgia and New Hampshire Avenues, and District police said the morning rush lasted until after 10:30 a.m. Police in the Virginia suburbs reported some snow-related backups.

Virginia-bound commuters had their big problem later in the day when a farmers' "tractorcade" -- not the weather -- tied up traffic heading for the bridges across the Potomac during the evening rush hour.

Almost 200 tractors driven by protesting farmers of the American Agriculture Movement filled the streets surrounding the White House, paralyzing traffic for several hours until D.C. herded the tractors back onto the Mall.

Potholes -- those axle-breaking cavities that appear in road surfaces in the aftermath of a snowstorm -- have proliferated throughout the metropolitan area, slowing traffic and putting scores of road crews to work at repairs.

In the District, Transportation Department Deputy Director B. J. O'Donnell said the Whitehurst Freeway and the Sousa, East Capitol Street and 14th Street bridges are among the hardest hit in the city.

Giant holes, some exposing the reinforced steel rods under the pavement, dotted the Whitehurst Freeway yesterday, forcing drivers to pick their way through like soldiers in a mine field.

Road crews with asphalt were on the freeway yesterday and Thursday attempting to patch the holes, but new ones appeared sometimes as fast as old ones were repaired.

Pothoies are especially difficult to repair while a thaw is in progress, O'Donnell said, because the cold asphalt mix used as a temporary patch tends "to come right out."

"You need dry conditions for a permanent patch with hot asphalt," he said, "and while the thaw is going on, the road surface is wet everywhere."

In the spring, "when it's warm and dry, we'll square the holes out and put (permanent) patches in," he said.

Potholes are caused, he said, by the "thaw-and-freeze cycle" cracking the road surface and allowing moisture to seep into the underlying concrete.

Bridges and other elevated roadways are especially susceptible to potholes, he said, because moisture mixed with salt from road spreaders "seeps through small cracks in the concrete and corrodes the reinforcing steel."

A chemical reaction between the salt and the reinforcing steel causes the concrete to "pop out," O'Donnell said, and a pothole is born.

O'Donnell said it is impossible to calculate how much money has been spent so far to repair potholes in the District. DOT road crews are paid whether they are filling potholes or doing other repair work, he said. In addition, however, the department's street maintenance budget for this year, includes about $300,000 for asphalt and $600,000 for private contract repair work, he said

While the National Weather Service and U.S. Geological Survey see no immediate threat of flooding, they are watching the situation closely.

Geological survey hydrologist Robert James noted that the Potomac River flow rate at Little Falls rose yesterday from 4 billion gallons a day at 8 a.m. to about 5.5 billion gallons at 4 p.m., still well below the normal flow level of 9 billion gallons a day at this time of year. Flood stage at Little Falls is 87 to 94 billion gallons a day.

"We're not anticipating flood stage," said James, even though forecasts call for scattered heavy rains to move through parts of the Potomac basin today. "Of course, you never can tell," he said. "The rain system could stall and dump it all right here."