The sedimentation of volcanic ash produced by explosive volcanic eruptions is commonly modelled as being governed by particles falling individually. However, collective settling processes, such as settling-driven gravitational instabilities can shorten the atmospheric residence time of ash. These instabilities generate downward-propagating plumes known as fingers that descend faster than the terminal fall velocities of ash particles, resulting in enhanced sedimentation that can affect deposit interpretations and dispersion forecasts. Despite being commonly observed below eruption plumes and clouds and in laboratory experiments, ash fingers are not yet described in ash dispersal models. Many previous experimental and numerical studies have examined finger formation in static configurations, leaving the influence of shear and turbulence in spreading ash clouds poorly constrained. In order to advance our understanding of SDGIs and tephra fallout, we experimentally investigated finger formation beneath buoyant particle-laden (40 μm glass beads) gravity currents in lock-release experiments to better simulate spreading volcanic plumes. By keeping constant the particle concentration in the gravity currents (1 g l ‐ 1 ) and varying the ambient fluid density, we modelled ash cloud spreading at different speeds, which creates interfacial shear and allowed us to assess the interaction between small-scale eddies and fingers using particle image velocimetry (PIV). Our results show that strong vortical motions suppress finger formation for high shear rates, whereas fingers can develop for weaker vortical motions generated at lower shear rates. Once formed, fingers descend at velocities comparable to the ones found in static configuration experiments despite elevated mixing and entrainment coefficient values (0.35 ± 0.19). Vorticity fields further reveal systematic asymmetry in the finger’s vortex rings, with negative (clockwise) vorticity dominating in most cases, which may reflect the residual vorticity inherited from the Kelvin-Helmholtz billows that develop at the interface during spreading. Together these findings highlight that vorticity influences both the likelihood of finger formation and their internal structure, reinforcing the need to incorporate ash finger dynamics into volcanic ash dispersion models.