In Leesburg this weekend, Blanche Dubois, the protagonist of Tennessee Williams' classic play, will ride the "Streetcar Named Desire" into a performance by the Blue Ridge Alliance of the Performing Arts, Loudoun County's well-established community theater, worth venturing out in the cold to see.

The anxious Miss Dubois brings to a lower-class neighborhood of New Orleans the shreds of her past: nightmares of her young husband, who shot himself after she caught him in bed with an older man; the deaths of four family members and her subsequent loss of their Mississippi plantation home; the long string of strangers at the Flamingo Hotel with whom she tried to regain some sense of feeling.

Soothing and comforting her is her only living relative, her sister Stella. Stella, meanwhile, has coped with new-found poverty by marrying a man of beefy build and torn T-shirt made famous by Marlon Brando: Stanley Kowalski.

Stanley is, as Blanche puts it in a rare burst of accuracy, an animal, an ape, a remnant from the Stone Age. And the relationship between them is one of executioner and victim, as Stanley demands first Blanche's money, then her dignity and ultimately her body in a tug-of-war over Stella's affections.

It is a play of pretense and reality, with Blanche desperately working to create the illusion of beauty and happiness that so long ago left her ("I don't want realism, I want magic"), and Stanley brutally thrusting the truth before her pained eyes ("I been onto you from the start").

It's a rough play, and one unsuited for young or amateur actors. So why did the Blue Ridge Alliance, known for pleasant comedies and lively musicals, take it on?

"We wanted to do a heavy," said co-producer Sharon Nelson, a backstage regular with the 14-year-old group. Coupled with productions of "Harvey" and "Cabaret" still ahead in their season, plus a children's theater run of the "Wizard of Oz" this summer, the group hopes to appeal to everyone in its vast audience. The alliance draws visitors from all over Northern Virginia and parts of Maryland and the District.

Performances are divided between Sterling Park and Leesburg, although most participants in this production live in the Reston/Sterling area, including the director, Pam McCoy. McCoy also designed the set, which depicts a cluttered apartment with a door to what one is forced to imagine is the largest bathroom in New Orleans. At one point, no less than four burly men disappear through that door in an attempt to sober up the drunken and raving Stanley.

The set also has a stage-walk across the back to represent the street outside the apartment, which McCoy fills effectively with passing vendors, whores and their customers, and a haunting-voiced blues singer (Cindy Kennon), to mark the passage of time.

The set is realistically shabby, but the upstairs couple (Linda Hendricks and R.B. Cummings), with their loud arguments and louder reconciliations, provide the proper tone of lower-class disrespectability.

Into this, Stanley (Tim Carlin) fits easily. Carlin's performance is fairly subdued, though he does very well in the tender scenes with his wife (Kimberly A. Stone).

Stone, unfortunately, acts more like a Reston resident in a community theater than a southern gentlewoman seduced in lower-class New Orleans.

The same cannot be said for her sister Blanche (Ann Stewart McDow). McDow's performance is slow in starting; she acts at first like just another imitation drunk in an imitation apartment. But as Stanley slowly unhinges her grip on the narrow ledge of reality, the audience draws nearer in sympathy and horror.

Then, when she describes the death of the only man she ever loved--her poor, perverted husband--the audience is pulled under by the waves of her misery, and we drown.

It is a performance powerful enough to make the play and fulfill the ambition of the theater group.

"A Streetcar Named Desire," by the Blue Ridge Alliance of the Performing Arts, Jan. 22 and 23, 8 p.m., J.L. Simpson Middle School, Leesburg. Tickets are $4 for adults, $3 for students and senior citizens. Call 430-9228 for information.