This episode's headline: Weather Forecasting. The guests include JAMES WITT, Independent Forecaster; DONALD GILMAN, National Weather Service; In Milwaukee (Facilities: WMVS-TV): GAIL MARTELL, Chief Meteorologist, E.F. Hutton & Co.. Byline: In New York: ROBERT MacNEIL, Executive Editor; In Washington: JIM LEHRER, Associate Editor; KENNETH WITTY, Producer; MAURA LERNER, Reporter