Northern Exposure Horns Wed.

 ((18), 10-11 p.m., CBS))

By JOHN P. MCCARTHY

Filmed by the Finnegan Pinchuk Co., Brand/Falsey Prods. and Universal TV. Exec producers, David Chase, Diane Frolov, Andrew Schneider; co-exec producers, Michael Vittes, Robin Green, Jeff Melvoin; supervising producers, Cheryl Bloch, Michael Fresco; co-producer, Martin Bruestle; consulting producer, Sam Egan; director, Fresco; writer, Melvoin; creators, Joshua Brand, John Falsey.
 
Cast: Rob Morrow, Barry Corbin, Janine Turner, John Cullum, Darren E. Burrows, John Corbett, Cynthia Geary, Elaine Miles, Peg Phillips, Paul Provenza, Teri Polo, Diane Delano, Simon Templeman, Gerard Ismael, Moultrie Patten, Earl Quewezance, James L. Dunn, Robert Nadir, Julie Sole, Robert Nicholson.
 

Northern Exposure's" 100th episode is evidence that TV's most cerebral feel-good show is in fine fettle, despite the long goodbye of Dr. Joel Fleischman (Rob Morrow). With the move to Wednesday night, ratings are a question mark.

Joel is released from his contract to stay in Alaska but decides not to return to Gotham. Clearly the producers are hedging their bets: He'll be just a canoe ride away.

The meat of the episode involves Cicely's bottled water. After seeing a pattern of genital abrasions and other sex-related injuries, Dr. Phil Capra (Paul Provenza) discovers there's something in the town's water. It makes women horny and aggressive while men take on feminine traits. The gender role-reversal yields some humor, and a unique explanation for the extinction of dinosaurs is offered.

Provenza and Teri Polo, as his wife, will probably win viewers over. The fish-out-of-water routine is workable, and Provenza makes an earnest straight man.

With Joel out of the picture, viewers may miss the tension between him and Maggie (Janine Turner), but regulars like deadpan Marilyn (Elaine Miles) and DJ-philosopher Chris (John Corbett) offer enough continuity. As a bonus, Officer Barbara Semanski (Diane Delano) offers a well-drawn, funny turn here.

Jeff Melvoin's writing is up to par, and the potentially trite gender stuff is dealt with briskly. Michael Fresco's direction is fresh. Tech credits are fine. Music is integral to "Northern Exposure" and David Schwartz delivers here.

The show's creative team has mastered the art of interweaving the individual and the communal.

But given the Wednesday competition and the show's gradual audience erosion, those facts may not be enough to keep the momentum going for "Northern Exposure."

Camera, Gordon C. Lonsdale; editor, Briana Spears London; production designer, Woody Crocker; art director, Kenneth J. Berg; sound, Robert Marts; music, David Schwartz.