The generation of two weak shock waves by a two-dimensional roughness mounted on the side wall of the test section of a wind tunnel and their influence on the supersonic boundary layer of a flat blunt plate is experimentally investigated at the Mach number 2.5. The measurements are made using a constant temperature hot-wire anemometer. In the boundary layer of the plate the profiles of the mean mass flow rate and the r.m.s. fluctuations are measured in the region of streamwise vortices generated by the pairwise weak shock wave upon the interaction with the flow in the vicinity of the leading edge of the model. High-intensity fluctuations generated by the influence of the weak shock wave are found to exist.