Abstract: A regional extreme snowstorm occurred in Jiangxi Province from 21 to 23 January 2024, accompanied by a return-flow weather pattern. The proportion of national meteorological stations experiencing snow accumulation reached 91.2%, the highest since 1959. The number of national meteorological stations with heavy snowfall were the greatest since 1991. Base on meteorological observation data and ERA5 reanalysis data, the circulation background, environmental conditions, and frontogenesis dynamical mechanisms of the return flow snowstorm was analyzed. The result are as follows. (1) Before the heavy snowfall event, the temperature gradually decreased from the lower to the middle atmosphere, with no inversion or cold layer observed. Warm-moist easterly return flow prevailed at 850 hPa. The specific humidity was 3–4 g·kg⁻¹ between 1,000 and 600 hPa. (2) The central and northern regions of Jiangxi Province exhibited prolonged warm and humid conditions between 500 hPa and the surface from 02:00 to 20:00 on January 22, 2024. The frontal genesis intensity at 700 hPa exhibited a high-value center extending northeastward from central Hunan to central-northern Jiangxi, with gradual intensification, promoting enhanced vertical upward motion. The pseudo-equivalent potential temperature (θse) at 700 hPa remained elevated (340–348 K), while a dense θse zone and frontal genesis center were observed near the 900–800 hPa level. Additionally, strong vertical ascent was identified within the low-level moisture transport belt in the return flow. These conditions contributed to favorable dynamic and thermodynamic environments for convective development. (3) During the snowstorm event, conditional symmetric instability was present. The area with MPV1≥1 PVU at 850 hPa extended northeastward from southern Jiangxi Province with gradually intensifying strength. The baroclinic term MPV2<0 PVU showed a low-value center that coincided with the MPV1 region. Vertically, the height of unstable energy generation was approximately at 700 hPa in northern Jiangxi and around 900 hPa in southern Jiangxi. The spatiotemporal distribution characteristics exhibited good correspondence with the snowstorm-affected areas.