A spring storm that spawned at least one tornado hammered the South with winds of nearly 100 m.p.h. and torrential rain, uprooting trees and utility poles, washing out roads and leaving Yorktown, Ark., ankle-deep in hail. In Laurel, Miss., winds clocked at 92 m.p.h. uprooted power poles, overturned three small planes and severely damaged the high school. A line of severe thunderstorms marched across Alabama, but no damage was reported. The northeastern corner of Arkansas was hardest hit by the eastward-rushing storm.