Mesoscale vortex usually stimulates local convection, which is an important system for persistent precipitation. The solution to the classical vorticity equation cannot directly describe and quantify the contribution of thermodynamic information to the development of vortices. In this study, the Boussinesq approximation is adopted to rewrite the vorticity equation, and the only forcing term employed is the vertical velocity potential vorticity. The form of this forcing term is similar to that of potential vorticity; however, vertical velocity is used instead of the potential temperature. Furthermore, the indirect effect of the thermodynamic process is introduced in the form of the horizontal pressure gradient to quantitatively describe the contribution of the dynamic and thermodynamic configurations to the vertical velocity potential vorticity equation. A heavy rain event, which occurred in southern Xinjiang on June 15, 2021, was selected as a case to analyze the transfer of low-level thermodynamic forcing to vertical vorticity using high-resolution numerical simulation data. The results showed that the local variation of the vertical velocity potential vorticity mainly originates from the coupling effect of the low-level vertical wind shear and low-level cold pool in the thermodynamic term, which contributed to a wide region of positive values ahead of the rainband. This pattern promotes the growth of vertical velocity potential vorticity in the corresponding region. The distribution and tendency of vertical velocity potential vorticity help maintain the positive vorticity ahead of the rainband, thereby making it conducive to the generation of strong ascending motion and new convection, directly leading to continuous precipitation.