This study examines the formation, evolution, and merger mechanisms of two meso-beta-scale vortices (V1 and V2) into a meso-alpha-scale vortex (V3) that triggered a heavy snowfall event over China's Loess Plateau on December 10-11, 2023. The merger of V1 and V2, occurring within the central region of an inverted trough northeast of the Tibetan Plateau, contributed similar to 71% of V3's initial cyclonic vorticity and intensified the snowfall event. Vorticity budget indicates distinct genesis pathways, with V1 forming primarily through horizontal vorticity advection and convergence-associated stretching, while V2 genesis was dominated by vertical stretching, with horizontal transport acting suppressively. After formation, V2 remained stretching-driven, whereas V1 shifted from stretching to horizontal-transport dominance. Kinetic energy budgets reveal that the strong southerly and southeasterly winds in the eastern inverted trough-critical for moisture transport-were sustained mainly by the pressure gradient force work, particularly its zonal component. The Fujiwhara-like merger of the two meso-beta-scale vortices, guided by their respective northwesterly (V1) and southeasterly (V2) mean flows, exhibited a dominant role of the pressure gradient force work in the kinetic energy budget. Key differences in wind acceleration mechanisms emerged, with the zonal component of the pressure gradient force work primarily enhancing westerlies in V1's southern half, while the easterlies within V2's eastern half shifted from zonal to meridional dominance in the pressure gradient force work during the merger process.