Cold air outbreaks (CAOs) are an important driver of near-surface baroclinicity at the entrance of the northern hemispheric storm tracks during boreal winter. They originate over the upstream continent in regions of surface radiative cooling, suggesting that this diabatic process is not only important for CAO formation, but potentially also a relevant contributor to downstream storm track variability. Here, we aim to provide mechanistic insights into the underexplored link between upstream diabatic cooling and storm track variability in the context of CAOs. For this purpose, we analyze and compare distinct subsets of CAOs, characterized by stronger and weaker diabatic cooling over Siberia, occurring over the Japan Sea in the 1979–2023 period. To investigate the potential role of upstream diabatic cooling on storm track activity after CAOs, we quantify modulations of Eady growth rate (EGR) in the western North Pacific. In addition, we quantify the impact of diabatic cooling on the Siberian High, a semi-permanent weather system that has previously been associated with the occurrence of strong CAOs at the entrance of the North Pacific storm track.</p> <p>With regards to low-level baroclinicity, we find that CAOs featuring enhanced upstream cooling are characterized by anomalously high EGR along the eastern coast of Russia and China. Further, peaks in EGR at the entrance of the storm tracks during winters between 1979–2023 are preceded by efficient radiative cooling over the continent, therefore contributing to a large temperature contrast between land and ocean. The contribution of diabatic processes to the intensification of the Siberian High is evaluated using the-sea level pressure (SLP) tendency equation. The diabatically driven SLP tendency at the time of maximum intensification amounts on average to 3.4 hPa 6h<sup>-1</sup>, and is of the same order of magnitude as the adiabatic contribution by horizontal and vertical motion. We also provide evidence that the land-based diabatic cooling indirectly supports, through baroclinic interaction, the amplification of an upper-level ridge-trough couplet that propagates into the storm tracks. The increased low-level baroclinicity and the deep upper-level trough at the entrance of the storm tracks, both enhanced by the upstream diabatic cooling, facilitate cyclogenesis at the entrance of the storm track. The resulting cyclones are more likely to be particularly deep, "bomb" cyclones and are associated with cyclonic wave breaking at upper-levels over the western North Pacific. On the other hand, we find no significant change in the number of cyclones developing in the 1–4 days following these CAO events: those subsequent cyclones remain small in size and do not exhibit strong intensification rates compared to climatology. In conclusion, our findings suggest that diabatic cooling over land takes an active role in shaping storm track variability, allowing us to mechanistically link upstream land–atmosphere thermodynamic processes to downstream extratropical cyclone activity.