  Using the tight-binding approach we study the electronic transport in a
$\mathrm{MoS}_2$ zigzag ribbon with a spatially varying potential profile.
Considering a ribbon with a smooth potential step in the Fermi energy regime
where the transport is dominated by the edge modes, we find that the
conductance exhibits sharp resonances due to the resonant transport through a
n-p-n junction effectively created in the structure. We show that in a gated
wire the current carried on the wire edges can be blocked despite the metallic
band structure of the ribbon. For the Fermi energies corresponding to
$\mathrm{MoS}_2$ bulk conduction band, we identify states of the semi-infinite
wire that are polarized in the $K$, $K'$, $Q$ valleys and exhibit the valley
Hall effect distinctly visible in a nonuniform ribbon. Finally, we show that
well-defined momenta of the valley polarized modes allow nearly complete valley
polarization of the current in a locally gated ribbon.
