Although serious questions remain about projected federal deficits, economists and investment advisers at T. Rowe Price Associates Inc. have formulated a fairly optimistic economic forecast for 1982.

But there was a first-the-good-news, then-the-bad-news quality about the forecast given by T. Rowe Price at its recent annual investment outlook seminar here.

From their offices overlooking Baltimore's Inner Harbor, the people at T. Rowe Price predicted a stronger economy beginning in the second half of 1982.

The firm's forecast is "consistent with the history of previous recessions and with what we consider to be the most likely case," said Ben E. Laden, vice president and chief economist at the securities firm.

Admittedly more optimistic than most forecasts at this point, T. Rowe Price's projections allow for some risk and volatility.

"If the deficit is still expanding in 1983 and 1984, we've got serious long-term problems," Laden conceded when asked about his forecast.

The range of outcomes is wider than usual, and "a high degree of confidence cannot be given to any particular numerical forcast," he added.

However, the odds favor a "bottoming" of the downturn in 1982, Laden said.

We are near the end of the downward trends in auto sales and housing starts, he pointed out, and by the spring of 1982 "both of those leading sectors will be rising in response to lower interest rates and improved availability of credit."

Nevertheless, recovery from the recession isn't likely to be as fast as the average rate of improvement in past periods, Laden believes. For example, interest rates are expected to remain higher "relative to the underlying rate of inflation," net exports are expected to decline, and government spending--particularly on the state and local level--"is likely to remain very weak."

T. Rowe Price's forecasts for the next few quarters include a sharp, 6 percent drop in the annual rate of real GNP in the final quarter this year. The company also expects a decline of 1.8 percent in next year's first quarter.

However, "we expect positive growth of 3 percent in the second quarter, followed by increases of 6.3 percent and 4.2 percent," Laden added.

Nonetheless, the forecast implies that real GNP will be unchanged on an annual average basis in 1982, he said.

Although T. Rowe Price continues to back the administration's program to lower inflation and boost economic growth, it appears to be in sharp disagreement over implementation of those policies.

At times, the administration's approaches to dealing with the economy have been "misdirected," Laden charged. Moreover, the president has made major concessions in the face of pressure from Congress in some instances, he said.

Thus far, the president hasn't squarely addressed reductions in social Security and defense spending, Laden remarked. And "until progress is made to control spending increases in these areas, the program cannot be expected to succeed."

It's possible that Reagan may not move to control spending in those areas until 1983, and a delay that long "could have an adverse effect on the markets," Laden suggested.

Meanwhile, the momentum that is expected in the second half of 1982 suggests an "improving investment climate" next year, observed T. Rowe Price Vice President Edward J. Mathias.

"We believe that substantial returns will accrue to investors who look beyond the next three to six months and position themselves so as to fully capitalize on a gradually improving investment environment," Mathias commented.

Recent declines in interest rates have enhanced the relative attractiveness of common stocks, he said.

Based on that assumption, T. Rowe Price's investment strategy is geared primarily to companies engaged in technology, energy, health care, financial services, defense and aerospace, and leisure activities--all described as growth areas of the '80s.

The outlook for the municipal bond market is also "quite good," said Peter J. D. Gordon, a vice president and fixed-income specialist.

Meanwhile, money market funds should continue to "hold their own" and possibly continue their assets growth despite prospects of declining interest rates and availability of more deposit instruments, concluded Vice President Edward A. Taber III.