An experimental realization of the two-dimensional problem of plane discontinuity breakdown during pulsed ionization of a flow region bounded by the surface of a shock in a channel was described. The experimental setup represents a shock tube with a measured cross section and the electric strength vector perpendicular to the flow velocity vector. The wave configuration incorporating shock waves traveling through the gas on both sides of the original discontinuity is formed as a result of the one-dimensional arbitrary discontinuity breakdown. A regime similar to the ideal discontinuity breakdown exists at the free end of the discharge interval for a manifold increase in the deposited energy density due to the discharge zone compression by the shock. The pressure in plasma sheets ahead of the shock is found to be greater than that in the volume part of the discharge.