  We show that the speed of the fastest coronal mass ejections (CMEs) that an
active region (AR) can produce can be predicted from a vector magnetogram of
the AR. This is shown by logarithmic plots of CME speed (from the SOHO LASCO
CME catalog) versus each of ten AR-integrated magnetic parameters (AR magnetic
flux, three different AR magnetic-twist parameters, and six AR
free-magnetic-energy proxies) measured from the vertical and horizontal field
components of vector magnetograms (from the {\it Solar Dynamics Observatory's
Helioseismic and Magnetic Imager}) of the source ARs of 189 CMEs. These plots
show: (1) the speed of the fastest CMEs that an AR can produce increases with
each of these whole-AR magnetic parameters, and (2) that one of the AR
magnetic-twist parameters and the corresponding free-magnetic-energy proxy each
determine the CME-speed upper-limit line somewhat better than any of the other
eight whole-AR magnetic parameters.
