The conventional observation data, NCEP/NCAR reanalysis data, and Doppler weather radar data are utilized to analyze the causes and the forecast error of the severe convective weather from 6 to 8 August 2016 in Weifang. The results are listed as below. 1) The trough at the bottom of the cold vortex at 500 hPa, the low vortex with shear line at 850 hPa, and the surface inverted trough are the main synoptic systems. The numerical forecast has a great deviation of the synoptic systems in this weather process, and the forecaster's high dependence on it is the main reason for the forecast error. 2) The strong water vapor convergence below 850 hPa is an important condition for the occurrence of the heavy precipitation. The strong ascending motion caused by the configuration of low-level convergence and high-level divergence is the dynamic mechanism of the heavy rainfall. The potential instability is strengthened by the sinking of cold air in the middle and upper levels. 3) The train effect and maintenance of the strong echo are important characters of the heavy rainfall, the development and movement of the upwind area is indicative to the location of the heavy precipitation. The mesoscale convergence line in the retrieval wind field from Doppler radar is a direct cause of the local heavy rainfall. 4) The horizontal wind field from wind profile radar can continuously display the vertical structure of the wind field and its changes during the precipitation process. The detection height obviously increases before the precipitation occurs, and the period of cold air intrusion at middle and high levels corresponds to the period of heavy precipitation.