The Prince William County Board of Supervisors yesterday parceled out about $1.3 million and more than 30 jobs to county agencies midway through its fiscal year.

County Executive Robert S. Noe Jr. said the fast-growing county expects about $1.2 million more from personal property taxes, local sales taxes and state funds this year than was projected. The surplus will go toward the expenses approved yesterday by the board, although the county probably will draw on its reserve fund to pay for the added items.

Noe warned, however, that the luxury of extra funds available at the county's midyear budget review is likely to be short-lived. He said the county can expect to encounter severe financial problems in fiscal 1986, starting July 1, largely because of about $12 million in capital projects the board has approved.

"We cannot accommodate everything painlessly," Noe said. He said the sessions in which supervisors will decide what projects to cut from the fiscal 1986 budget are "going to be bloody . . . more bloody than I can describe."

In a lengthy presentation to the board, Noe said the county might be forced to finance some of the capital projects through bond issues. He acknowledged later, however, that Prince William voters have a history of rejecting referendums on bond issues.

The capital projects include a number of one-time expenses and construction, such as a recreation center and new county office building in eastern Prince William.

Noe said the county may be forced to seek new sources of income to augment real estate taxes. He mentioned the possibility of imposing a business, professional and occupational license tax, as well as increasing revenues from cigarette and meal taxes.