<p>The western North Pacific anticyclone (WNPAC) is an important system influencing the winter weather and climate in East Asia. Its formation and maintenance mechanisms have been extensively discussed across subseasonal and interannual timescales. However, the mechanisms regarding the synoptic variations of the WNPAC, which are closely linked to extreme weather, remain less well understood. In this study, an extreme case of WNPAC development is examined to investigate the key factors driving its changes on the synoptic timescale. Results show that synoptic variations of the WNPAC can be driven by the cold surge in East Asia. The WNPAC forms during the outbreak (cooling) period of cold surges and further strengthens in decay (warming) period, suggesting a complex influence of cold surges on WNPAC evolution. The formation of WNPAC in the cooling period is primarily attributed to the dynamic processes associated with the southward expansion of Siberian High. While during the warming period, thermal effects dominate the strengthening and vertical deepening of the WNPAC. Using a simplified two-layer diagnostic framework, we demonstrate that adiabatic heating in the mid-troposphere and diabatic heating in the lower troposphere jointly contribute to the WNPAC intensification during the warming period. Futher analyses of large-scale circulation reveal that the mid-tropospheric adiabatic heating in warming period is also indirectly linked to cold surge, as the intrusion of cold air into the tropics enhances subsidence within a local meridional circulation.</p>