David Patterson of Lutherville, Md., played 2-under-par golf and overwhelmed Frank Edwards of Martinsville, Va., 5 and 4, to win the 12th annual Bobby Bowers Memorial Junior yesterday at Springfield Golf and Country Club.

Karen Jefferson of Seaford, Del., became the first repeat champion in the girls division. She won the last two holes and defeated good friend Tara Hipp of Gaithersburg, 1 up.

Last year Patterson finished a narrow second for region junior of the year honors. After winning this tournament, winning his second Gorin tournament last week and placing second in the South Atlantic Junior, "I'd say he's almost got locks on it already" for 1986, said his caddie, Ken Lampard.

Patterson birdied the first hole yesterday and never looked back. The Maryland state high school champion (representing Dulaney) birdied the 12th hole to go 5 up and ended the match at the 14th, where both he and Edwards birdied.

"He never let down at all," said Edwards, a junior at Woodberry Forest. "He didn't hit but one bad shot the whole round."

Jefferson was 1 down to Hipp going to 17, but rolled in a 40-foot birdie there, then won at the par-4 No. 18 after Hipp pushed her second shot into a greenside bunker and took double bogey.

Brian Quackenbush of Herndon won the 14-15 division, Tim Burnett of Rockville the 13-and-under.

Virginia State Open: Six-time state amateur champion Vinny Giles shot 4-under-par 68 for a one-shot lead opening the 72-hole, $50,000 event at Richmond's Willow Oaks.

"I haven't really played good golf since 1976," said Giles, 43, of Richmond, whose last big triumph was the British Amateur 11 years ago.

Pro Bruce Lehnhard of Fredericksburg fashioned a 69, Richmond amateur champion Hugh Powell and pro Woody FitzHugh of Reston 70s. FitzHugh aced No. 7.

Md. Women's Amateur: Two victories apiece yesterday advanced Sarah LeBrun of Green Spring and Tina Barrett of Sparrows Point to today's final at Chevy Chase Club.

In the semifinals, LeBrun defeated Wendy Kern of Talbot, 5 and 4, and Barrett defeated Lois Ledbetter of Lakewood in 20 holes.

Recently in the Baltimore Metropolitan Women's Championship, Barrett defeated LeBrun.