Rob Morrow makes his final appearance on "Northern Exposure" tonight.

Really.If you've been keeping up with the show for the past few months, you might have thought so before. As a matter of fact, you might have thought so several times before.

And that's been a huge mistake. The show has been so obsessed with the departure of Morrow's character, Dr. Joel Fleishman, that it's been like a car spinning its wheels while stuck deep in the mud. It just hasn't gone anywhere.

In retrospect, the producers would should have just let Morrow go and moved on. It would have been better for the series. As it is, the show is pretty much out of ideas and out of steam.

"Northern Exposure" is a series that was fresh, different and wonderful when it came on the air as a summer tryout back in 1990. And when it made it back on the schedule in early 1991, the magic was still there.

The fish-out-of-water story featuring the New York doctor (Joel) dropped in this strange and wonderful world of Cicely, Alaska, was an absolute delight. Funny, smart, offbeat and entertaining, it was one of the best shows on television.

But, as with so many shows that burst out of the blocks on a creative high like that, the question of maintaining that quality loomed in the background. And, after the first couple of seasons, the unfortunate answer to that question was that the show could not keep it up.

Let's face it, "Exposure" had two really great seasons and it has been running on fumes ever since.

It's no longer fresh. The offbeat characters that were so much fun have grown stale and predictable.

Instead of taking a slightly off-kilter view of the world, "Exposure" too often strains to be different and ends up just being strange. Worse yet, it's all-too-often boring.

The departure of Morrow isn't the blow that will kill the show. It's been terminally ill for some time.

Fans of the show will want to tune in tonight (9 p.m., Ch. 5) to see that departure, however. After a slow start, a plot line that finds Joel dragging Maggie along on his search for a fabled lost city is indeed a nice sign-off for Joel.

Oh, there are some misfires along the way - some annoying detours, and a surprise appearance by a semi-regular character that is nothing more than a stunt that doesn't work well at all.

But the payoff at the end is worth the wait. There's a lovely, touching farewell between Joel and Maggie, and Joel's ultimate departure makes sense - in a strange, Cicely sort of way.

However, "Exposure's" other problems can be clearly seen in the episode's other two plot lines. In one, the ever-annoying Chris (John Corbett) sues the town's new doctor (Paul Provenza) for malpractice, while the doctor's journalist wife (Teri Polo) gets an assignment to write a restaurant review of the Brick.

The two stories seem oddly familiar, like we've seen this too many times on "Northern Exposure" before. And, furthermore, the episode points up just how poorly these two new characters have been integrated into the fabric of the series.

Morrow's departure could have been an opportunity for a series in sad need of some freshening up. A chance to take the show in some different directions.

But, largely thanks to the is-he-gone-or-isn't-he stories involving Joel, none of the opportunities have been taken advantage of.

Is there still hope for "Northern Exposure?" Maybe, but not much.

The move to Wednesdays, which has been accompanied by a precipitous drop in "Exposure's" ratings, is not a sign of confidence on the part of the CBS programmers.

And, when all is said and done, maybe it would be better for "Exposure" to ride off into the sunset while it still has a little bit of self-respect remaining.

It's still an OK show. Better it should be remembered for its first two seasons than for what is now - and what it might become as it winds down even farther.