  The interstellar medium is a multiphase gas in which turbulent support is as
important as thermal pressure. Sustaining this configuration requires both
continuous turbulent stirring and continuous radiative cooling to match the
decay of turbulent energy. While this equilibrium can persist for small
turbulent velocities, if the one-dimensional velocity dispersion is larger than
approximately 35 km/s, the gas moves into an unstable regime that leads to
rapid heating. I study the implications of this turbulent runaway, showing that
it causes a hot gas outflow to form in all galaxies with a gas surface density
above approximately 50 solar masses/pc^2 corresponding to a star formation rate
per unit area of 0.1$ solar masses/yr/kpc^2. For galaxies with escape
velocities above 200 km/s, the sonic point of this hot outflow should lie
interior to the region containing cold gas and stars, while for galaxies with
smaller escape velocities, the sonic point should lie outside this region. This
leads to efficient cold cloud acceleration in higher mass galaxies, while in
lower mass galaxies, clouds may be ejected by random turbulent motions rather
than accelerated by the wind. Finally, I show that energy balance cannot be
achieved at all for turbulent media above a surface density of approximately
10^5 solar masses/pc^2.
