Mary Cervi, whose house was turned into rubble Wednesday night while she was cleaning the dinner dishes, sat in a neighbor's kitchen yesterday discussing what hit her.

"Do you know what a split second is? There was no cracking; there was no giving way of beams. Just boom. That's it," said the ashen-faced woman.

Cervi's four-bedroom, $150,000 house in Fairfax County was spread out over the block as she spoke, its pink insulation hanging in bushes and aluminum siding wrapped around trees.

The house, at 9511 Baccarat Dr., was one of 22 homes near W. T. Woodson High School, located on the edge of Fairfax City, that was severely damaged by a tornado born of Tropical Storm David. The area was described by officials yesterday as the most severely storm-damaged neighborhood in the Washington metropolitan area.

Fortunately, Mary Cervi did not live in the subdivision near the crest of a hill on Little River Turnpike seven years ago when the area felt the bomb-like impact of Tropical Storm Agnes. That storm ripped the roofs off the high school and a supermarket and sent countless trees flying into cars and homes.

In 1972, Paul Mayo, who lives directly across from the Woodston football field, was lucky. His home suffered only minor roof damage then. Yesterday his roof was in his backyard swimming pool. Mayo, a CIA analyst, was calling his neighborhood a "windy hill."

The tornado that tore into "windy hill" Wednesday at 7:22 p.m. caused an estimated $2 million in damage to more than 165 structures in Fairfax County and Fairfax City. One man was killed elsewhere in the county and another was seriously hurt near Woodson High.

The tornado, according to county officials, moved in a northerly arc across the county; striking first at the Woodley-Nightingale Trailer Park on U.S. Rte. 1 south of Alexandria, touching down again near Woodson High and cutting a swath of destruction across four housing developments in Fairfax City. It then touched down again in the Great Falls area near the Potomac River.

Virginia Gov. John N. Dalton, who on Wednesday night declared a state of emergency for the entire state, flew to Fairfax County yesterday afternoon to survey storm damage. Answering questions from local officials, Dalton said he could not yet promise state or federal aid to families without insurance.

As the politicians discussed who pays for the reconstruction, the storm victims picked through their windblown and rain-soaked belongings, stopping sometimes to stare blankly at the mess.

As she was resting, Mary Cervi explained yesterday what she and her family did after the tornado splintered much of their house.

"My home was gone. I was hysterical. There was plaster and pieces of wood on top of me. I started screaming for my husband," she said.

Frank Cervi, a patent examiner for the U.S. Patent Office, said he yelled back for his wife, and frantically began shoving away the rubble that had fallen on top of him.

When the tornado hit, Cervi had been sitting at the kitchen table with his son, March, 18, his daughter Kathy, 22, and her fiance, Jeff Preuss.

By shouting above the roar of the wind, Cervi said he located some of his family and began clearing a narrow passageway so they could get out of the house.

"I was tearing and clawing in the rain. I cut my hand on a piece of glass," said Cervi. The cut required 18 stitches to close.

After they were out of the house, Cervi realized his youngest daughter, Carol, 14, was still inside. She was cowering in a corner of a downstairs bathroom.

"The poor thing. She was scared to death," said Mrs. Cervi. She said her daughter finally came out of the bathroom after she was assured it was safe outside.

As the Cervi family began to dig out of the rubble, Paul and Frances Mayo on nearby Whitacre Road heard what they described as a "buzz saw" headed straight for their living room picture window.

Frances Mayo said the sky turned black and a 60-foot oak tree in the front yard was uprooted and thrown toward the house.

"I turned and screamed, "Honey, get the kids to the basement quick." We fell over top of each other getting the kids downstairs.

"We beat the tornado by two seconds. There was a roar and it was gone. I never heard the roof leaving the house," she said.

The Mayos lost their roof, a covered walkway, a carport, and a tool shed. Pillows from their sectional sofa flew into neighboring yards.

As she and her family lay waiting in the basement after the tornado passed, Frances Mayo was frightened by the sizzle of raindrops hitting bare electrical wiring. "It was a soft, eerie sound after all the noise," she said.

As the tornado moved past Woodson High and into Fairfax City, it took the roof off several units of the Lyndhurst Apartments. City officials yesterday condemned 37 units there, forcing residents to relocate for at least 30 days.

Tallie Bethoun, who lives in a $245-a-month, one-bedroom apartment in the complex, was among the homeless.

"Once you leave here at 6 p.m. tonight, Mr. Bethoun, I don't know when you will be allowed to return," the apartment manager, Florence Lee, told him. "You can't be lucky everytime, Mr. Bethoun. The storm missed us last time."