  We apply the recent wavepacket formalism developed by Ossadnik to describe
the origin of the short range ordered pseudogap state as the hole doping is
lowered through a critical density in cuprates. We argue that the energy gain
that drives this precursor state to Mott localization, follows from maximizing
umklapp scattering near the Fermi energy. To this end we show how energy gaps
driven by umklapp scattering can open on an appropriately chosen surface, as
proposed earlier by Yang, Rice and Zhang. The key feature is that the pairing
instability includes umklapp scattering, leading to an energy gap not only in
the single particle spectrum but also in the pair spectrum. As a result the
superconducting gap at overdoping is turned into an insulating pseudogap, in
the antinodal parts of the Fermi surface.
