Mayor Marion Barry received a somewhat chilly sendoff from the White House last week as he departed on his three-week trip to Africa.

Even as the mayor was packing his bags for Monrovia, Liberia, the Reagan administration was leaking word that among the budget items to be frozen next year are the federal payment to the District of Columbia and money to operate the St. Elizabeths mental hospital.

The news was a stinging blow to the mayor, who only weeks before had boasted that he wouldn't need a tax increase to balance his fiscal 1986 budget proposal, which will be unveiled early next year.

The mayor's budget experts apparently were counting on at least a modest increase in the federal payment, which is paid annually to the District because of the large amount of tax-exempt federal property and constitutes about 16 percent of the District's total general operating funds.

D.C. officials also assumed that compromise legislation approved by Congress this year to transfer St. Elizabeths from the federal government to the city by 1991 would provide adequate federal funding to assure a smooth transition.

Under the congressionally approved St. Elizabeths agreement, the city would receive a total of $219 million in funding and special assistance to operate the hospital over the next six years, before assuming total control.

Ronald C. Willis, the senior mental health specialist for the House District Committee who has closely followed the long-running St. Elizabeths controversy, said that a freeze of any kind on funds for the hospital would be "absolutely devastating."

Willis said that a freeze on either the regular appropriation or the special funds would throw off the plan for the transfer and lead to a sharp reduction in the quality of care for patients and the possible loss of accreditation.

Likewise, a freeze on the federal payment could wreak havoc with D.C. finances in the coming year.

Although city officials have long complained about the uncertainty of the federal payment, which to a large degree depends on the whims of the White House and Congress, in fact there has been a steady increase in the payments throughout the Carter and Reagan administrations.

Congress approved a federal payment totaling $425 million for the current fiscal year. Without a further increase next year, Barry must consider the equally unpleasant prospects of program cuts or tax increases -- even with the projected 5 to 7 percent growth in D.C. revenues because of the economy.

Barry's 1986 budget proposal is not likely to include capital improvement funds to expand the D.C. Jail or Lorton Reformatory, despite recurring problems of crowding and violence within the city's corrections system.

For philosophical and budgetary reasons, the mayor says, he is unalterably opposed to spending additional money to build new prison facilities.

Yet the latest crisis of crowding and violence at Lorton, stemming from last week's emergency doubling-up of nearly 400 inmates from the Youth Center No. 1 with prisoners in Youth Center No. 2, may prompt some sharp questioning from members of the D.C. City Council when they review the mayor's construction budget.

City Council member H.R. Crawford (D-Ward 7), who has proposed the creation of a blue-ribbon panel to design a new jail and choose a site for it, said that the city has no choice but to expand its facilities.

Crawford says that the city, as a good neighbor, should feel obliged to do something to relieve the tensions and problems at Lorton, which for years have left residents of the surrounding Fairfax County community nervous and upset.

Moreover, the D.C. corrections system must get ready to handle the expected influx of prisoners who will be sentenced under the District's voter-approved determinant sentencing law.

"We put the cart before the horse in adopting that legislation ," Crawford said this week. "We said, 'Lock them up.' But we have no place to put them . . . . Cost now is no consideration. We must carry out the law."

City Council Chairman David Clarke said that it is possible the issue will be brought up during the council's review of Barry's 1986 capital improvements budget. But, for the time being, Clarke says he senses no groundswell of support among his colleagues for a new jail or prison.