  We present an implementation of Higgs boson production via vector-boson
fusion in association with three jets at hadron colliders in the POWHEG-BOX, a
framework for the matching of NLO-QCD calculations with parton-shower programs.
Our work provides the means to precisely describe the properties of extra jet
activity in vector-boson fusion reactions that are used for the suppression of
QCD backgrounds by central jet veto techniques. For a representative setup at
the CERN LHC we verify that uncertainties related to parton-shower effects are
mild for distributions related to the third jet, in contrast to what has been
observed in calculations based on vector-boson fusion induced Higgs production
in association with two jets.
