Montgomery County law enforcement officers are searching for a convicted rapist who escaped Wednesday from the county jail in Rockville by digging under a gate and tossing jackets on top of a barbed-wire fence before scaling it.

The absence of Kenneth F. Joppy, 27, was discovered about 12:04 a.m. yesterday when an inmate alerted guards during a routine inmate count at the Detention Center, said Claire Gunster-Kirby of the county Department of Correction and Rehabilitation.

Joppy apparently escaped by hiding in a storage closet adjacent to the recreation yard. Officials speculate that Joppy used a snow shovel from the closet to dig under a gate on the southwest side of the yard. He then used denim inmate jackets from the closet to scale the jail's barbed-wire fence, Gunster-Kirby said.

Joppy, who faced a possible life sentence on a first-degree rape conviction this fall, was last seen by a guard around 4 p.m. Wednesday in the jail's outdoor recreation yard, Gunster-Kirby said. Joppy was among about 50 inmates in the yard from 2:30 to 4 p.m. that day for supervised recreation, she added.

A police helicopter and ground search in the vicinity of the jail on Seven Locks Road early yesterday failed to locate Joppy, Gunster-Kirby said. Authorities said they think that Joppy, a Gaithersburg resident, was unarmed.

Corrections officials said the escape is the first from the county jail since 1981. Gunster-Kirby said department officials are investigating whether proper security procedures were followed.

Gunster-Kirby said Joppy's escape apparently was "well thought-out." Officials are investigating whether other inmates were involved.

Joppy, whose last known address was the 12400 block of Suffolk Terrace, was convicted in September of raping a 35-year-old Silver Spring woman while posing as a roof repairman. According to court records, Joppy tied the woman with a telephone cord and diapers after assaulting her. He is scheduled to be sentenced Jan. 29.

Joppy, who according to court papers has an "extensive criminal record for arrests for peeping Tom, robbery, residential burglary, weapons and drug offenses," is scheduled to be tried in February on charges of attempted first-degree rape, robbery and theft in an alleged attack on a 47-year-old Wheaton woman.

Paul Korman, who lives across from the county jail, said he was "distressed that the person was gone for eight hours without discovery."