The structure and dynamics of a small (10 km) but vigorous mesoscale vortex is described with high-resolution multiple Doppler radar observations. The vortex was associated with dissipating deep convection within an intense squall line, which represented the primary component of the MCS over northern Alabama. The vortex persisted within the stratiform region of the MCS for more than one hour. Vortex formation was similar to that of line-end tilting of vorticity, combined with stretching between the residual updraft and strong downdraft. The maximum vortex rotational velocity of 21 m/s (within the 3-4 km AGL layer) is comparable to moderately intense mesocyclones in supercell storm. As vertical motion subsided within the vortex, hydrometeors acted as passive tracers and showed a distinct swirl in reflectivity patterns. Despite the small diameter of 10 km, this vortex is best classified as a mesoscale convective vortex.