Based on the conventional observation data, the 0.25°×0.25° FNL data, microwave radiometer data and the wind profile radar data, the circulation features, atmospheric junction characteristics in two return-flow weather processes that occurred in southern Jiangsu Province were analyzed. Results show that the synoptic situation of 500 hPa in the high latitude area is two troughs and one ridge, the near-surface layer is continuously affected by the northeast wind, the southwest warm and wet airflow climbs up along the bottom cold pad, which is a situation of return-flow snowfall weather. The cold air flowing southward from the northeast plain has little humidity and only plays the role of "cold cushion" in the precipitation. The differences of the southwest warm and wet airflow in the middle and low troposphere lead to different snowfall intensities of the two processes; the cooling near the surface layer has a greater impact on the discrimination between rain and snow, statistics of eight snowfall cases in southern Jiangsu Province from 2012 to early 2022 find that the possibility of snowfall should be considered in southern Jiangsu Province when meeting the temperature threshold conditions of T₈₅₀ ≤ -4℃,T₉₂₅ ≤ -3℃,T_{1 000} ≤ 1℃,T_2m ≤ 2℃; when 1 515 gpm ≤ H_700-850 ≤ 1 575 gpm, 1 289 gpm ≤ H_{850-1 000} ≤ 1 317 gpm, the phase changes from rain to snow. The strengthening of the southwest airflow in the middle and low troposphere and the bottom northeast wind, the transformation of the wind field at the height of about 2 000 m, the short-wave trough (or shear line) trigger the release of unstable energy, which leads to the occurrence of snow; when the southwest airflow weakens and turns to northwest airflow, water vapor content of the atmosphere decreases and the snowfall ends.