Co‐Occurring Weather Systems Vary by Atmospheric River Scale Across the United States

Abstract Atmospheric Rivers (ARs) often co‐occur with other weather systems, including fronts, low‐pressure systems (LPSs), and mesoscale convective systems (MCSs), which can amplify precipitation and flood risk. While extreme rainfall is frequently linked to multiple interacting features, how these systems co‐occur with AR intensity scales and regions remains unclear. Using ERA5‐derived feature masks and satellite data, we quantify spatiotemporal overlaps between ARs and other systems. AR + Front combinations dominate across much of the conterminous U.S. In higher AR scales (4–5), more complex MCS‐related combinations become increasingly common, particularly in DJF and MAM and along the West Coast, while limited LPS‐related co‐occurrences appear mainly in JJA and SON and are confined to regions such as the Gulf of Mexico and offshore Pacific genesis regions. In contrast, AR‐only occurrences dominate in some inland western regions. Extreme precipitation exhibits seasonal variation, with distinct co‐occurring systems contributing across seasons.