Steve Metcalfe drama is an adroit three-character post-Vietnam story

Strange Snow

Play by Steve Metcalfe. Directed by Thomas Bullard.

''Strange Snow'' displays the humor, tenderness, and also the awkwardness of its three characters. Steve Metcalfe's comedy drama begins noisily when Megs (Dann Florek) creates the kind of commotion he hopes will awaken his wartime buddy, David (Christopher Curry), for their early morning date to go fishing. But unfortunately David is sleeping off his latest binge. It is his spinster sister, Martha (Kaiulani Lee), who answers the door, golf club at the ready, to subdue a suspected burglar.

Instead, the clumsy but likable Megs winds up persuading Martha to join the fishing excursion. From this point on, ''Strange Snow'' becomes on one hand a romantic comedy about Megs and Martha. On the other hand, it concern the laying of ghosts which have haunted Megs and David since their battle experiences in Vietnam and their loss of a cherished buddy. The more mature Megs has found at least a degree of inner peace and self-reconciliation, but David's solution has been to attempt to drink his traumas away.

Mr. Metcalfe interweaves the parallel themes with sufficient adroitness to command the spectator's concern for his suddenly entangled trio - particularly Megs and Martha. Aided by Mr. Florek's and Miss Lee's winningly sympathetic performances, the developing relationship between extrovert garage owner Megs and the reticent schoolmarm Martha proves appealing and believable. It is not a new situation, but it works. Mr. Curry does what a good actor can do with the less well-defined part of David, who - until almost the end of the play - seems not so much a victim of war as of his own selfish surliness.

The play also suffers at present from a certain lack of clarity about what actually happened to the two friends in Vietnam and about certain relevant family matters. The ending, too, seems pat and formulized. What recommends ''Strange Snow'' is its basic humanity and the credibility of its affirmation. The world premiere of Mr. Metcalfe's latest work at the Manhattan Theater Club Upstage has been well served in the production directed by Thomas Bullard, with scenery by Atkin Pace, costumes by Nan Cibula, and lighting by Cheryl Thacker.