WASHINGTON (UPI) The National Science Foundation says it may be possible to control weather and climate by putting vast artificial clouds into the sky. It also holds out hope that potential tornadoes, and hail and lightning storms may be converted into gentle rains by cloud-seeding. The foundation emphasized yesterday, however, that much more atmospheric research must be carried out before the answers can be found ‘‘to the complex questions involved in weather modification. ’ The agency made weather modification research grants of $1.1 million in fiscal 1959. Grants for the current fiscal year ending June 30 will total slightly more than the 1959 figure.