I present a theoretical investigation of the temperature and magnetic field dependence of isotropic (paranematic) wetting layers close to an aligning substrate within a semi-infinite nematic liquid crystal with positive magnetic anisotropy under condition of weak homeotropic anchoring. Using the Landau-de Gennes model supplement by Nobili-Durand surface free energy, the existence and stability of paranematic wetting layers close to the substrate and below the nematic-isotropic temperature are discussed. Numerical results are presented showing the phase diagram for the isotropic (paranematic), nematic, and wetting layer states. In the present work, the dependence of the transition kind to the magnetic field is discussed.