  The [OIII] 5007 A emission line is the most common tracer of warm, ionized
outflows in active galactic nuclei across cosmic time. JWST newly allows us to
use mid-infrared spectral features at both high spatial and spectral resolution
to probe these same winds. Here we present a comparison of ground-based,
seeing-limited [OIII] and space-based, diffraction-limited [SIV] 10.51 micron
maps of the powerful, kiloparsec-scale outflow in the Type 1 red quasar SDSS
J110648.32+480712.3. The JWST data are from the Mid-InfraRed Instrument (MIRI).
There is a close match in resolution between the datasets (0."6), in ionization
potential of the O$^{+2}$ and S$^{+3}$ ions (35 eV), and in line sensitivity
(1e-17 to 2e-17 erg/s/cm$^2$/arcsec$^2$). The [OIII] and [SIV] line shapes
match in velocity and linewidth over much of the 20 kpc outflowing nebula, and
[SIV] is the brightest line in the rest-frame 3.5-19.5 micron range,
demonstrating its usefulness as a mid-IR probe of quasar outflows. [OIII] is
nevertheless intriniscally brighter and provides better contrast with the
point-source continuum, which is strong in the mid-IR. There is a strong
anticorrelation of [OIII]/[SIV] with average velocity, which is consistent with
a scenario of differential obscuration between the approaching (blueshifted)
and receding (redshifted) sides of the flow. The dust in the wind may also
obscure the central quasar, consistent with models that attribute red quasar
extinction to dusty winds.
