  We present a search for associated production of Higgs and $W$ bosons in
$p\bar{p}$ collisions at a center of mass energy of $\sqrt{s}=1.96$ TeV in 5.3
fb$^{-1}$ of integrated luminosity recorded by the D0 experiment. Multivariate
analysis techniques are applied to events containing one lepton, an imbalance
in transverse energy, and one or two $b$-tagged jets to discriminate a
potential $WH$ signal from standard model backgrounds. We observe good
agreement between data and background, and set an upper limit of 4.5(at 95%
confidence level and for $m_H=115$ GeV) on the ratio of the $WH$ cross section
multiplied by the branching fraction of $H \rightarrow b \bar{b}$ to its
standard model prediction. A limit of 4.8 is expected from simulation.
