Arlington County will receive $4.3 million more in revenues next fiscal year than county officials previously estimated, lowering the county's projected deficit from $6.7 million to $2.4 million, a new county staff report predicts.

County Manager Larry J. Brown, in a report prepared for Saturday's County Board meeting, said revised revenue estimates based on a reevaluation of spending and income in the first four months of this fiscal year, mean the county could stick to its current budget guidelines that call for a $174.2 million budget next year. That budget includes $50.7 million for county schools and $16.1 million for the Metro system.

Brown said the county is expecting a $4.5 million balance in its general fund at the end of this fiscal year because inflation is dropping, vehicle fuel prices are stabilizing, worker compensation costs are leveling off and repairs to the Thomas Jefferson Community Center's roof cost less than expected.

The county also is expecting $1.2 million in other revenues, principally through the gasoline and personal property taxes. However, it is also projecting a $1.4 million revenue shortfall, in part attributable to the sluggish real estate market that has slowed the growth of assessments.

The county still will face a deficit that Brown said "has been narrowing and can be managed . . . by either increased revenues, new revenues, program reductions or a combination of all three."

In approving the budget guidelines last month, the board told Brown to prepare a balanced fiscal 1984 budget that would allow the county's real estate tax rate of 98 cents per $100 of assessed valuation to be maintained.

"I certainly feel we should be able to find a couple of million dollars without raising taxes," said board member Dorothy T. Grotos yesterday. "Every year we start out with gloom and doom with these projections and every year we end up with a sizable surplus carryover."

Though many uncertainites remain, such an the amount of federal aid to the county, Brown said the estimates assume that national economic trends such as lower interest rates and inflation will continue in the foreseeable future.

Brown also predicted that the financial picture could be improved later next year if mortgage interest rates drop, stimulating the market and leading to higher assessments.