Lloyd Vernon Mitchell, 57, a Defense Department meteorologist with more than 30 years of government service, died Tuesday at Tucson Medical Center in Tucson, Ariz. He had suffered from a heart ailment.

Mr. Mitchell was born in St. Louis, Mo., and graduated from Southern Illinois University in Carbondale, Ill. He began his career as a weather man during World War II service with the Army Air Corps. He was stationed in Washington and remained here after the war as a civilian meterologist.

At the time of his retirement in 1974 for reasons of health, he was chief of the rocket sonde branch of the environmental technical applications center at the Washington Navy Yard Annex. The branch studies the upper atmosphere for its effects on the weather.

Mr. Mitchell, who moved to Tucson from his home in Hillcrest Heights shortly before his retirement became effective, was a member of the American Meterological Society, the American Society of Geographers, and the D.C. chapter of the Southern Illinois University Alumni Association.

In Tucson, he was active with the senior adult ministries of the Arizona Southern Baptist Convention.

Survivors include his wife, Thelma G., of the home in Tucson; a daughter, Melba M., also of Tucson, and a son, Gregory L., of Hyattsville.

The family suggests that expression of sympathy be in the form of contributions to the Lloyd V. Mitchell Memorial Fund, Twenty-Second StreetBaptist Church, Tucson 85710.