Abstract: To prevent and mitigate the possible adverse effects of heavy snowfall on facility agriculture, production and life, and to improve the level of snow forecast, 19 regional snowstorms in Nantong since 1951 were analyzed from impact systems, atmospheric temperature stratification, dynamic and water vapor conditions by using conventional high altitude and surface data and ECWMF 0.75°×0.75° reanalysis data. The diagnostic analysis and forecasting process were illustrated with the regional snowstorm in 2013 as an example. The results showed that: (1) Nantong belonged to the north subtropical monsoon climate, and the process of rain or sleet to snowstorm accounted for the majority; to judge the snowfall, we should pay attention to the precipitation after snowfall, and the surface temperature for estimating the depth of snow cover, therefore, we must consider the comprehensive influence of strong cold air downward and strong warm and humid air flow northward; (2) the synoptic systems of heavy snowfall mainly included two westerly troughs, one in the north and the other in the south, as well as mid-low level shears, southwest jets and low-level cold cushion, the example was a typical regional snowstorm weather situation; (3) there were at least two strong SW jets at 500- 850 hPa altitudes, and the strong convergence rise mainly occurred at 700 hPa and above, which provided dynamic and water vapor condition for the formation of snowstorm; the cold cushion was below 850 hPa, and there was a temperature inversion between 850 and 700 hPa; when the air temperature of 850 hPa was ≤-4℃ and air temperature of 2 m level was ≤3℃, the precipitation changed to snow, and the snow cover increased obviously after the surface temperature approached zero; (4) the average 24 h SLR (snow to liquid ratio) in Nantong was more than 10 in pure snowfall snowstorm, the process of rain or sleet to snowstorm was less than 10, and that in the southeast was less than 5, and the precipitation phase transition and SLR could be generally prejudged by air temperature of 850 hPa, and temperature of 2 m level and surface; (5) it was also a feasible method to find the similar process of weather situation from the historical heavy snowfall, compare stratification, dynamic and water vapor conditions, and then enlarge or reduce the snowfall and snow depth of similar processes to infer precipitation and snow depth.