The unpredictable variability of the ionospheric F region greatly limits the efficiency of communications, radar and navigation systems which employ high frequency (HF) radiowaves. The objective of this work is to forecast the ionospheric critical frequency values (foF2) one hour in advance. For this a novel method has been developed for 1-hour ahead forecasting of the critical frequency of the F2 layer (foF2) based on applying feedback on predicted monthly median values of foF2 for each hour. The basic model for the prediction of the monthly medians consists of a parabolic dependency on R12 superimposed by a trigonometric expansion in terms of the harmonics of yearly variation, linearly modulated by R12. The monthly medians for each hour are predicted by applying the basic model over a sliding data window. ¿ 2000 American Geophysical Union