Simpson’s last show likely will be Friday, people on both sides said, barring any last-minute changes to an exit agreement that was still being finalized over the weekend.

The Washington Post reports Simpson’s contract does not expire until March 2011. But his exit deal allows him to leave on Friday. The agreement also says the radio host will not be allowed to work at another station for the next 13 1/2 months.

CBS will keep Simpson from jumping to another station by invoking the “non-compete” provision of his contract. The clause bars Simpson from working for a Washington-area station for the next 13 1/2 months. CBS invoked a similar provision in 2008 when another of its local personalities, Don Geronimo, left WJFK-FM before his contract had expired.

Simpson’s departure follows months of declining ratings for his show and internal friction between Simpson and WPGC’s management. The station has sought to boost Simpson’s ratings and attract younger listeners by updating his playlist and playing hit songs more often. Simpson and his producer-son, Donnie Jr., have maintained that the station was meddling, compromising his long-running program and alienating loyal listeners.

CBS had wanted to ease Simpson out with a celebratory retirement party in mid-March, but Simpson declined, according to people familiar with the negotiations between him and the station. Late last week he began telling listeners on the air that his departure was imminentDonnie Simpson is a longtime American radio DJ as well as a television and movie personality. He has hosted The Donnie Simpson Morning Show on Washington, D.C. radio station WPGC-FM since March 1993. Simpson is the first urban-format radio personality to have an annual salary over $1 million without being syndicated. He was Billboard’s “1998 Air Personality of the Year”. He is also known by the nickname “Dr. Green Eyes” for his luminous light green eyes.

Simpson began his career at age 15 at Urban Contemporary radio station WJLB in Detroit, Michigan, where he remained for eight years. In 1977 he relocated to Washington, D.C., where he began working at WRC-FM, known as “Disco 93.9” (now WKYS), as morning drive host and program director. He remained with WKYS for 15 years through its format migration from Disco-based Rhythmic Contemporary Hits to Urban Contemporary in the 1980s. In 1981, he was hired as back-up anchor for the George Michael Sports Machine sports show on NBC’s Washington television outlet, WRC-TV.