i will describe joint work with jared wunsch on propagation of singularities for some semiclassical schrodinger equations where the potential has singularities normal to an interface. semiclassical singularities of a given strength propagate across the interface, but only up to a threshold. this is due to diffracted singularities which are weaker than the incident singularity by a factor depending on the regularity of the potential. time permitting, i will give applications to logarithmic resonance-free regions in scattering theory.