  Scattering in the ionized interstellar medium is commonly observed to be
anisotropic, with theories of magnetohydrodynamic (MHD) turbulence explaining
the anisotropy through a preferred magnetic field direction throughout the
scattering regions. In particular, the line of sight to the Galactic Center
supermassive black hole, Sgr A*, exhibits strong and anisotropic scattering,
which dominates its observed size at wavelengths of a few millimeters and
longer. Therefore, inferences of the intrinsic structure of \sgra\ at these
wavelengths are sensitive to the assumed scattering model. In addition,
extrapolations of the scattering model from long wavelengths, at which its
parameters are usually estimated, to 1.3 mm, where the Event Horizon Telescope
(EHT) seeks to image Sgr A* on Schwarzschild-radius scales, are also sensitive
to the assumed scattering model. Past studies of Sgr A* have relied on simple
Gaussian models for the scattering kernel that effectively presume an inner
scale of turbulence far greater than the diffractive scale; this assumption is
likely violated for Sgr A* at 1.3 mm. We develop a physically motivated model
for anisotropic scattering, using a simplified model for MHD turbulence with a
finite inner scale and a wandering transverse magnetic field direction. We
explore several explicit analytic models for this wandering and derive the
expected observational properties --- scatter broadening and refractive
scintillation --- for each. For expected values of the inner scale, the
scattering kernel for all models is markedly non-Gaussian at 1.3 mm but is
straightforward to calculate and depends only weakly on the assumed model for
the wandering of the magnetic field direction. On the other hand, in all
models, the refractive substructure depends strongly on the wandering model and
may be an important consideration in imaging Sgr A* with the EHT.
