A new concept of a thermally induced local circulation is presented by numerical and observational studies. This wind system transports a low-level air mass from a plain to a basin, passing over a mountain ridge. The characteristics of the wind system are investigated using two- and three-dimensional numerical models. Upslope winds develop over the mountain slopes surrounding the basin until late afternoon. These winds are composed of separate individual circulations both inside and outside the basin. The atmospheric temperature in the boundary layer within the basin becomes higher than that outside, so that the surface pressure becomes lower at the bottom of the basin than that outside. At dusk, the thermal forcing due to the surface heat flux decreases, weakening the upslope winds, and then a plain-to-basin wind develops over the mountain ridges due to the pressure difference formed in the daytime. The plain-to-basin circulation is generated when the altitude of the mountain range is almost equ... Abstract A new concept of a thermally induced local circulation is presented by numerical and observational studies. This wind system transports a low-level air mass from a plain to a basin, passing over a mountain ridge. The characteristics of the wind system are investigated using two- and three-dimensional numerical models. Upslope winds develop over the mountain slopes surrounding the basin until late afternoon. These winds are composed of separate individual circulations both inside and outside the basin. The atmospheric temperature in the boundary layer within the basin becomes higher than that outside, so that the surface pressure becomes lower at the bottom of the basin than that outside. At dusk, the thermal forcing due to the surface heat flux decreases, weakening the upslope winds, and then a plain-to-basin wind develops over the mountain ridges due to the pressure difference formed in the daytime. The plain-to-basin circulation is generated when the altitude of the mountain range is almost equ...