  We derive the distribution of interferometric visibility for a source
exhibiting strong diffractive scintillation, with particular attention to
spectral resolution at or near the Nyquist limit. We also account for arbitrary
temporal averaging, intrinsic variability within the averaging time, and the
possibility of spatially-extended source emission. We demonstrate that the
interplay between scintillation and self-noise induces several remarkable
features, such as a broad "skirt" in the visibility distribution. Our results
facilitate the interpretation of interferometric observations of pulsars at
meter and decimeter wavelengths.
