Unsuccessful forecasting for two snowfall processes in Beijing in 2011 is analyzed by using a variety of high spatial temporal resolution observation data, NCEP1°×1°analysis data, and conventional observation data. The result shows: (1) On 29 November 2011, one of the most important reasons that there was no snow in Beijing is that the east winds in Beijing were dry and cold in a deep layer, and the boundary layer moisture condition was unfavorable. The cold air moved southward, leading to a filling pressure trough in the lower troposphere, which is another important reason for the fault prediction. (2) In the process of snowfall on 2 December 2011, the front and 925 hPa shear line provided dynamic condition for uplifting boundary layer water vapor convergence, and the lower troposphere water vapor transmission provided the moisture condition for snow. (3) Comparative analysis shows that more attention should be paid to water vapor change in the boundary layer in snow forecasting in Beijing. It hardly snows even if there is obviously favorable weather pattern but poor water vapor condition in the boundary layer; it probably snows if there is good moisture condition and convergence in the boundary layer, even if there were no favorable weather systems in the middle troposphere.