Swissair will lower its midweek apex fares to Switzerland, starting Jan. 15. The new fares will be valid Monday through Thursday until the end of March. Travel from New York will be $557; from Boston, $552, and from Chicago, $617.
Swissair is also lowering all ski land packages by 10 percent. More information about these packages is available in a brochure, ''Alpine Experience ,'' from Swissair.
For more information and brochures, contact the Swiss Center, 608 Fifth Avenue, New York, N.Y. 10020.