A blockbuster program at Lisner Auditorium last night brought to a close what has turned out to be the most diversified and artistically the strongest City Dance series since the festival's beginning four years ago. Certainly last night's finale was a smasheroo.

The evening began with the Washington Ballet, performing "Variations Serieuses" by the company's resident choreographer Choo San Goh. This neoromantic abstraction for 12 dancers, set to the Mendelssohn piano music of the same title, was created in 1977 and revived as recently as this past season. In previous accountings it has always appeared a rather pallid composition -- deftly structured but a mite academic. It looked wholly transformed in last night's inspired performance, however, and with its newly acquired sharpness of contour and expressive nuance, the ballet reveals itself as one of Goh's most compelling creations.

The choreography, in responding to Mendelssohn's wistful melancholy, contains more passages of lyrical repose that occur in Goh's better known, typically propulsive works, and it is lyricism of a very sensitive species. Moreover, the shaping of the whole ballet as a poetic analogue of the score discloses Goh's musicality at its finest. Half of last night's metamorphosis was ascribable to newly achieved understanding by the dancers; the other half was due to pianist Clinton Adams' sturdily passionate rendering of the music.

The Glen Echo Dance Theater, making its City Dance debut, played its strongest suit -- the choreography of Pola Nirenska, who was not only lured out of "retirement" (she's 71) to stage some of her earlier work for the company, but has even made a new dance this year for the same group. "The Divided Self," the new work, was given its premiere Wednesday evening at Lisner; with its potent schizoid tensions made visible, it combines the true grit of earlier modern dance epochs with the unspoiled creativity of Nirenska's present. For last night's program, the Glen Echo dancers -- who perform like demons under Nirenska's tutelage -- paid further homage to their mentor with luminous interpretations of her "Three Sculptures" and "Double Concerto."

Completing the evening's triumph was the appearance of the African Heritage Dancers and Drummers, who've graced every City Dance since the start and who've made a veritable habit of excellence. Melvin Deal, the troupe's director, led five men, with Yakub Addy heading the superb drum contingent, in "Bambaya," a bristling social dance from Ghana that adumbrated the American Twist. Then the men, women and six incredible children of the ensemble presented "Chiwara," a stunningly colorful, complex and virtuosic harvest rite that had the timbers shaking. The audience -- with every good reason -- went completely wild. The Opening

The first of two major City Dance '81 programs at Lisner Auditorium Thursday night drew an exceedingly enthusiatic, if moderately sized, crowd. The turnout was understandable given that the event was more or less competing against itself, since the festival sampler taped by WETA Wednesday evening was showing on the air, for free, the same evening as this larger live performance -- an inexplicably self-defeating idea from the outset. l

The program's jubilant opening was provided by the D.C. Youth Ensemble, one of three troupes appearing under the City Dance banner for the first time this year. The ensemble, directed by Carol Watkins-Fostser, consists of 40 high school students from the metropolitan area. Founded in 1980, it has already carved a unique niche for itself in the Washington dance scene.

The group, in fact, might be nicknamed "the Watkins-Foster miracle." The director-founder not only whipped these teen-agers into amazing dance fitness in record order, but is also responsible for the savvy, exhilarating and shrewdly proportioned choreography of such numbers as "If My Friends Could See Me Now," the stylized disco jamboree that kicked off the Lisner program. If City Dance '81 had done nothing else than give the D.C. Youth Ensemble this well-deserved exposure, it would have justified its expense.

The principal attraction of the Hoffman Dance Consort, also new to the festival, is its dancers, who are attractive, spirited and skillful. Strongest testimony to their appeal came in the "Stravinsky Quartet," Daniel West's neatly amusing piece about a bored young man and the three sirens who try to heat up his daydreams; West was the man, and Fernanda Setubal, Eleanor Bunker and Beth Spicer were the charmers.

A festival high point was the premiere of a new opus, commissioned for City Dance, by Raquel Pena, one of the nation's paragons of Spanish dance who happens to reside and work here. "Zapateado de la Garrocha," Pena's latest, used Spanish cowboy motifs in costuming, props and dance imagery to confect a brilliantly designed flamenco number capped by a sizzling solo cadenza for the masterful Pena herself. Pena and three others of her troupe, along with guitarist fernando Sirvent and singer Pepe do Cadiz, expertly performed two additional repertory pieces as well.

The Maryland Dance Theater, looking rather wearied but characteristically polished all the same, presented "Joint Venture" and "Doing the Dance," with especially fine work coming from Sandra Pollock and Alvin Mayes.