WARRENTON, VA., SEPT. 1 -- Snowden Clarke, aboard Passion, won the schooling jumper class after a six-horse jumpoff tonight as the 91st annual Warrenton Horse Show wrapped up its third day of competition with classes in conformation, working hunters and schooling jumpers.

In second place behind the winner's time of 37.22 seconds was Edgar Pagan, riding Viruloso, in 37.76. Susan Runco, owner and rider of Hialeah Colors, clocked 38.11.

According to Clarke, of Rock Ridge Farm in Middleburg, Va., who has ridden Passion for only two weeks, the course and the competition were difficult. "It's not a Grandprix but every course is difficult," he said. "There was a lot of galloping between the fences and that always makes for exciting competition."

Set in the shadows of the Blue Ridge Mountains, the Warrenton show is one of the oldest Virginia traditions. According to Matt Collins, trainer and owner of Mane Farm in Culpeper, the show perennially draws a large contingent of local horses and riders. Of the almost 400 entries in the four-day competition, approximately one-fourth are from nearby farms.

But Collins, like most people who will attend this year, comes every year because of the show's prestige and quality. Warrenton is an A-rated show.

It does indeed attract riders from all over the country. Primarily, though, it's a place where home folks pull their cars up to the ring and watch from the tailgate, where spectators from other area farms come to watch their friends and neighbors compete. They gather with picnic baskets full of gourmet food, or just potato chips.

The Warrenton show does, according to some regulars, have limitations such as only one ring, whereas most shows have graduated to three. This is the first year that bluestone, a fine-grade gravel, has been used in the ring. In past years the ring has been a natural surface. The bluestone provides more secure and consistent footing. FRIDAY-SATURDAY RESULTS

First- and Second-Year Green Working Hunter -- For Many Reasons (32.5 points), Cismont Manor Farms, Keswick, Va., Mr. and Mrs. Julian Heron. Reserve champion, Rose To The Occasion (25 points), Fox Mill Farm and Mr. and Mrs. C.W. Holmberg, High Point, N.C.

Green Conformation Hunter -- For Many Reasons (41 points). Reserve champion, Salishon (35 points), Warrenton, Va., Louisa Lenehan.

Working Hunter -- LeStat, Alison Firestone, Waterford, Va. Reserve champion, Country Clever, Evelyn Cowles.

Local Hunter Other Than Rider -- Winter Magic, owned by Nemo Nieman, Culpeper, Va., ridden by Winn Reid. Reserve champion, Yellow Brick Road, Diane Fiore and Partners Hill Ltd., Middleburg, Va., ridden by Mary Boos.

Owner-Rider Local Hunter -- Simbalu, Sue Attisani, Middleburg, Va. Reserve champion, Kildare, Diana Firestone, Waterford, Va.

Best Young Horse -- Shades Of The West, Cismont Manor Farm, Keswick, Va.; 2nd, Peace And Quiet, Cismont Manor Farm.

Colts/Geldings -- Unnamed entry, Diana Dodge and Nokomis Farms, Montpelier Station, Va.

Fillies -- Stellar, Louisa Lenehan, Warrenton, Va.

2-Year-Old Colt/Gelding -- Shades Of The West; 2nd,Fleetwood Thom, John Davis.

2-Year-Old Filly -- Nechako, Nokomis Farm; 2nd, Kachina Doll, Cismont Manor Farm.

3-Year-Old -- Just Me, Kathryn Borsody.

Broodmare -- Le Chocolat, Little Run Farm; 2nd, Wave Crest, Mrs. R. Braga and Mrs. P. Brown.

Breeding Champion -- Peace And Quiet; 2nd, Royal Fairy Tale, Margaret Fullington.

Yearling Colt/Gelding -- Peace And Quiet; 2nd, Ronnie's Choice, Mrs. R. Braga and Mrs. P. Brown.

Yearling Filly -- Royal Fairy Tale.