Thunderstorms erupted over the southern plains for a second day with heavy rain and winds up to 70 m.p.h. Winds clocked at 70 m.p.h. lashed Goodnight, Tex., and winds gusting to 50 m.p.h. in Waco blew down the "Big Top" at Reed Brothers Circus before a crowd arrived for performances. Officials also were investigating whether the storms were to blame for the crash of a private airplane near Austin, which was believed to have killed four people. In the East, the rain prompted the National Weather Service to issue flood watches for Maryland, West Virginia, Virginia and North Carolina.