Abstract:One snowstorm process in January 19-20, 2011 was analyzed by using Doppler radar data from Jiujiang and Nanchang, observation data and NCEP reanalysis data (0.5°×0.5°). The results showed that the ascending of strong and ample warm wet southwest airflow ahead of south trough and along the low level return cold airflow over the Yangtze River Basin is the dynamic mechanism responsible for this heavy snow. The secondary circulation is produced by the coupling of low and upper level jets. The positive vorticity advection over 700 hPa and the low level warm advection denote the strong upward motion. The stable θse isoline dense section at 700 hPa indicates that the frontal zone is maintained. The low level warm advection, the increase of wind velocity in the middle and lower level and the decrease of jet stream center are good indices for the enhancement of snow echoes. The low level warm advection structure develops into cold advection structure, indicating the snow echoes get weakened. The abnormal high radar reflectivity is not caused by large water droplets and solid precipitation particles such as hails. Ice crystals melt as they fall through warm layer above 0℃ coalescing, aggregating and growing by themselves, which leads to abnormal high radar reflectivity similar to large water droplets, without convective weather such as thunders. The strong upward motion in the middle and lower troposphere and the feedback mechanism of latent heat create partial high radar reflectivity, so producing the snow storm.