Profits of the Washington Post Co. in the first quarter this year rose 32 per cent from the same period in 1976, the communications firm reported yesterday.

Allegheny Airlines, meantime, reported a loss of nearly $11 million in the recent quarter, which was adversely affected by bitter cold weather.

Post Co. first-quarter earnings totaled $5 million (57 cents a share) compared with $3.8 million (42 cents) in the same 13 weeks a year earlier. Revenues increased more than 18 per cent to $94.6 million.

Ultimate profitability of the Post Co. was unusually affected by two developments in the first quarter of 1976 - strikes against The Post newspaper here and a newsprint manufacturing affiliate in Canada, which hurt the year earlier profits and a nonrecurring gain of $1.8 million (after taxes) from the sale of a radio station in Cincinnati.

The company estimated that a strike against the Washington newspaper, which began Oct. 1, 1975, and was concluded substantially in mid-February last year, caused an estimated $2 million reduction of revenues for the 1976 first quarter and reduced before tax profits by $1.3 million.

In the recent quarter, the Post Co. said all three major divisions reported higher revenues and before-tax profits.

Although the firm did not provide data on divisional profits, the earnings statement yesterday said newspaper division revenues were up nearly 28 per cent, while profits before taxes "improved substantially." The company publishes The Post and the Trenton, N.J., times.

Advertising linage increased nearly 16 per cent for The Post and 8 per centat the New Jersey newspaper during the recent quarter, the company said.

Newsweek magazine division revenues were up nearly 13 per cent in the quarter, reflecting higher circulation and advertising rates. Broadcasting revenues rose 6 per cent over the 1976 period.

Allegheny Airlines, the nation's sixth largest domestic carrier, reported a first-quarter loss of $10.9 million compared with a smaller loss of $8.9 million for the same period last year.

The Washington-based firm normally reports a loss in the winter quarter and profits as weather gets warmer.

In the first three months of 1977, however, severe weather conditions depressed profitability more than anticipated although revenues rose to $102.7 million from $93.4 million. The loss for March was $609,000, an improvement from the $642,000 loss a year ago.

Baltimore Gas & Electric Co., which plans to appeal a decision of the Maryland public service commission last Friday, ordering $32 million of refunds to customers, reported a decline in first-quarter profits to $30.8 million from $34 million in the 1976 period. Revenues rose to $228 million from $203 million.

The Baltimore utility blamed increased expenses, including operations at its Calvert Cliffs nuclear generating plants, for the reduction in profits.

Reports for the first quarter from area banks were as follows (net income before securities gains or losses):

First & Merchants Corp., a Virginia bank holding company, $2.1 million (64 cent a share) vs. $2 million (61 cents).

Bank of Virginia Co., a record $2.9 million (62 cents) vs. $2.75 million (60 cents).

Dominion Bankshares Corp., $2.71 million (43 cents) $3.01 million (48 cents).

Equitable Bancorporation, a Baltimore-based holding company. $2.35 million (67 cents) vs. $2.1 million (60 cents).

Mercantile Bankshares Corp., another Baltimore holding company, $2.27 million (50 cents) vs. $2.21 million (48 cents).

Arlington Trust Co., $650,549 ($1.87) vs. $586,645 ($1.68).