  We used the Tycho-Gaia Astrometric Solution catalogue, part of the Gaia Data
Release 1, to search for candidate astrometric microlensing events expected to
occur within the remaining lifetime of the Gaia satellite. Our search yielded
one promising candidate. We predict that the nearby DQ type white dwarf LAWD 37
(WD 1142-645) will lens a background star and will reach closest approach on
November 11th 2019 ($\pm$ 4 days) with impact parameter $380\pm10$ mas. This
will produce an apparent maximum deviation of the source position of
$2.8\pm0.1$ mas. In the most propitious circumstance, Gaia will be able to
determine the mass of LAWD 37 to $\sim3\%$. This mass determination will
provide an independent check on atmospheric models of white dwarfs with helium
rich atmospheres, as well as tests of white dwarf mass radius relationships and
evolutionary theory.
