Federal Reserve policy makers will meet this week in the midst of enormous uncertainty about what the New Year will bring and what the central bank's monetary policy ought to be.

For weeks, many financial market participants have expected a substantial easing of monetary policy, such as a cut in the 7.5 percent discount rate -- the interest the Fed charges on loans to financial institutions. No easing of that magnitude has occurred, and there are indications that none is likely as a result of the two-day meeting of the policy-making group, the Federal Open Market Committee, or FOMC, that begins on Monday.

Without a cut in the discount rate, most short-term interest rates are unlikely to fall much below their current levels, analysts say. Long-term interest rates have been declining in anticipation of smaller future federal budget deficits and dropping oil prices, while short-term rates have been virtually stable for four months.

The key consideration for the FOMC's 10 voting members -- there is one vacancy and Fed Gov. Henry C. Wallich is ill -- will be the state of the economy.

Reports from the 12 Federal Reserve districts, a forecast by the Fed's Washington staff and the expectations of a number of FOMC members all indicate that the economy will continue to grow in a subdued way, probably at a 2 or 3 percent pace in the coming six months.

"The economy appears to be growing slowly at best," says the summary on current economic conditions in the districts, which was prepared for the meeting. "Only Richmond the district that includes Washington and Baltimore describes its district economy as strong, although there is some optimism in the reports from Philadelphia and New York.

"Retail sales gains are uneven, and less-than-robust Christmas sales are expected. Auto sales are low now that special interest-rate incentives have largely ended. Industrial activity continues quite sluggish, with few gains yet from dollar depreciation.

"Residential construction is improving, but nonresidential construction is uneven. Agricultural prices remain weak despite some rises in meat prices; agricultural land prices continue to fall, and farm finances remain weak. Commercial bank consumer and real estate lending is rising further, but business lending is declining in most districts," the summary says.

The FOMC also will hear a forecast from the Federal Reserve Board's Washington staff that calls for an increase in the gross national product, adjusted for inflation, of between 2 and 3 percent in the first half of 1986, sources say.

However, the Reagan administration continues to project real GNP growth of 4 percent or a little less during 1986. And some private forecasters, such as Joel Popkin and Michael Evans, who head Washington economic consulting firms, expect even stronger growth than that, particularly in the next six months.

Earlier fears at the Fed that the value of the U.S. dollar on foreign exchange markets might fall so rapidly as to cause an inflation surge have receded but not disappeared. "So far, the dollar has been declining in an optimum way," says Fed Vice Chairman Preston Martin.

Recent statements by Martin and other FOMC members, as well as interviews, suggest there will be a division of opinion at the meeting Monday similar to that at other recent meetings:

Martin appears likely to continue to seek a somewhat easier policy stance and lower interest rates. In a recent speech, Martin declared, "The major risks I foresee for next year are on the down side, in part because of continuing signs of economic weakness." However, he adds, "I think we were given a little relief" with somewhat faster economic growth in the third quarter when the gross national product, adjusted for inflation, rose at a 4.3 percent annual rate.

Fed Governor Martha R. Seger, who remains concerned about "a sluggish economy" and the aging of the recovery -- "The older it gets, like humans, the more vulnerable it is to ailments and shocks," she says -- is likely to push hard for a policy easing.

Meanwhile, Robert P. Black, president of the Richmond Federal Reserve Bank, who has dissented from the majority at the last two FOMC meetings, wanting a somewhat more restrictive policy to curb overly rapid growth of the money supply, might do so again. Growth of the measure of money that Black follows, M1 -- which includes currency in circulation and checking deposits at financial institutions -- slowed in October but shot up again at a 13 percent annual rate in November and remains well above the Fed's target range.

Between these differing views is the FOMC majority, led by Chairman Paul A. Volcker. The members' positions shade one into another, but the essential ingredient is a balancing of risks.

One member who has voted with the majority consistently, Fed Governor Emmett J. Rice, said he expects the economy to grow at about a 2 1/2 percent rate in the first half of 1986 and inflation "to come in under 4 percent."

Rice said that combination "doesn't make me uncomfortable. It doesn't make me happy, but it doesn't make me uncomfortable.

"I don't think there is much we can do to speed up growth," he explained. "Anything we might do to stimulate the economy might give us problems later. Money growth is faster than I would like. Interest rates have come down . . .

"Obviously opinions differ, even here. Interest rates could fall further, and they will, on the basis of what has been done so far. But an activist policy of stimulating the economy right now would entail risks that are larger than I want to take. Obviously I am talking about more inflation pressures that might emerge if we embark on an activist policy.

"In short, I think we have given the economy as much room as it needs. Any push for growth will have to come from elsewhere, such as faster growth in other countries," Rice declared.

At its last meeting, the FOMC formally decided not to tighten policy to slow M1 growth sufficiently to bring it within its target range for the fourth quarter. While no other member seems to share Black's view of the importance of that monetary aggregate, several members remain concerned about its rapid growth.

They also are worried by the even faster rise in private debt in the United States, fearing it will leave American households and businesses vulnerable to any interruption of economic growth.

Another member of the FOMC majority, Governor J. Charles Partee, whose term expires at the end of January and who therefore may be attending his last FOMC meeting, shares much of Rice's outlook.

Running through what is happening in various sectors of the economy, Partee concluded, "I don't think it adds up to much of a plus in the next several quarters, and I really don't know what can be done about it."

Partee worries about the host of problems facing the nation's financial system -- such as problem loans in commercial real estate, energy and agriculture and the debt problems of developing nations. "I hope we can continue to show some modest gains in economic activity, or otherwise I don't know what we will find out," he said.

At the same time, Partee expressed concern about the growth of the money supply and of debt. "We could be storing up excess liquidity against a future time, and we may have to move against it. We could have no alternative unless one is willing to take serious risks with inflation," he said.

Martin warned in his speech that a failure to begin reducing federal budget deficits could help precipitate a recession next year. One major question with which the FOMC will have to deal is what weight to give to the Gramm-Rudman-Hollings federal budget deficit reduction bill that became law last week.

The new law mandates deficit-lowering actions at about a $20 billion annual rate beginning in March and more than twice that figure for fiscal 1987, which begins in October. Moreover, earlier measures in the second quarter of this year began to shift the budget in the direction of restraining, rather than stimulating, the economy, some analysts believe.

Volcker and other Fed officials long have appealed for lower deficits and, although they have made no concrete promises, members of Congress and financial-market participants have assumed that an easier monetary policy would be adopted once the deficits were put on a declining track.

Gramm-Rudman-Hollings -- which calls for a $144 billion deficit in fiscal 1987 rather than the $200 billion or more commonly forecast by private economists -- already has affected financial markets. As it neared passage, long-term interest rates fell significantly. Analysts said two major factors behind the slide were the expectation that the federal government would be borrowing less in the future and that the Fed would seek to lower interest rates, which remain at historically high levels compared to inflation.

But should the FOMC believe deficits will fall anywhere near as sharply as promised by Gramm-Rudman-Hollings? The law's constitutionality already has been challenged in court, and there is no mechanism to force Congress or the president to meet its various deadlines for action.

The basic divisions among members of Congress and the president that have led to repeated impasses over how to reduce deficits have not been eliminated. For instance, when Congress adjourned for the weekend, it still had not passed a promised "reconciliation" bill that would reduce spending and increase revenue by about a combined $20 billion. And President Reagan, opposed to the revenue increases and some other parts of the bill, has threatened to veto it.