  Pulsar glitches, sudden jumps in frequency observed in many radio pulsars,
may be the macroscopic manifestation of superfluid vortex avalanches on the
microscopic scale. Small scale quantum mechanical simulations of vortex motion
in a decelerating container have shown that such events are possible and
predict power-law distributions for the size of the events, and exponential
distributions for the waiting time. Despite a paucity of data, this prediction
is consistent with the size and waiting time distributions of most glitching
pulsars. Nevertheless a few object appear to glitch quasi-periodically, and
exhibit many large glitches, while a recent study of the Crab pulsar has
suggested a cut-off deviations from a power-law distribution for smaller
glitches. In this paper we incorporate the results of quantum mechanical
simulations in a macroscopic scale superfluid hydrodynamics simulation. We show
that the effect of vortex coupling to the neutron and proton fluids in the
neutron star naturally leads to deviations from power-law distributions for
sizes and from exponential distributions for waiting times. In particular we
predict a cut-off in the size distribution for small glitches.
