A linear, empirical low-order-model was developed with the aim of describing the evolution of a vortex-pair ejected into a boundary layer. The model combines a counter-rotating pair of LambOseen vortices in the proximity of a wall with a cross-flow Blasius boundary layer. Two inputs from experimental measurements are used. First, the initial locations where the vortices form, and pinch-off from the excitation slot boundary layers. Second, the time evolution of the vortices' circulation in still-air. With this input the model predicts the trajectories and vorticity distribution during the interaction. Such a model could be a viable tool for the development of a low-order-model to be implemented as a simplified boundary condition in CFD simulations, with the aim of reducing the requirement to fully resolve the vicinity of the excitation slot in active flow control simulations.