The present space-based solar observing facilities, such as the Helioseismic and Magnetic Imager (HMI) instrument aboard the Solar Dynamics Observatory (SDO) satellite, can obtain time series photospheric vector magnetograms of solar active regions with high spatial and temporal resolution. The time evolution of the photospheric vector magnetic fields can be traced continuously for nearly all active regions appearing on the solar disk except for the marginal area near the solar limb. This facilitating condition is a huge benefit to the solar flare forecasting. By numerical modeling of the coronal magnetic fields based on the sophisticated nonlinear force-free field model from the observed photospheric vector magnetograms, the time series data of the coronal magnetic fields corresponding to the time series photospheric vector magnetograms can also be obtained. Then, the numerical analysis can be performed on the coronal magnetic field data, and the time evolution of the internal coronal magnetic structures as well as the evolution of the nonpotentiality in solar active regions can be revealed. The deduced quantitative measures of the coronal magnetic fields from the numerical analysis, such as the electric current density, the force-free factor, and the magnetic energy density, can be utilized in the solar flare forecasting and for establishing the solar flare prediction model. Samples of electric current analysis are presented. Through the numerical analysis of the time series magnetic fields in solar active regions, it is expected to predict flare locations, flare classes, and timing of flares.