Abstract: Using the WRFV3.2.1 mesoscale numerical model, a return-flow snowstorm process occurred on November 9-12, 2009 in Hebei province was analyzed based on the 1°×1°NCEP-FNL reanalysis data four times a day. The characters of the return-flow snowstorm and its physical mechanism were discussed according to the products from the above model. The results indicate that the surface ground is cold cushion generated by dry and cold air mass. The warm-wet airflow transports from the lower level to upper level along the upper boundary of front surface. The occurrence of snowstorm is related with transportation of high temperature and high humidity energy, and water vapor is mainly from the south. Anticyclone and divergence area is main area near the ground surface, and strength of ascending motion?corresponds to?the activities of?mesoscale convective cloud mass.  The rainfall intensity increases because of the effect of topography of Taihang Mountain

Key words: Return-flow snowstorm, Numerical simulation, Diagnostic analysis