Heavy, widespread, and persistent precipitation events are among the most important atmospheric hazards in northwestern Iran, and understanding the synoptic mechanisms responsible for their formation and persistence is of considerable importance. This study aimed to identify and analyze the synoptic patterns responsible for the longest-lasting heavy and widespread precipitation events in northwestern Iran. For this purpose, daily precipitation data from 58 synoptic stations were examined during the period 1980–2021. To identify heavy precipitation, the 90th percentile of daily precipitation amounts at each grid cell was used as the threshold, while the 75th percentile of positive precipitation-area anomalies was considered the threshold for spatial extent. Subsequently, consecutive periods of heavy and widespread precipitation were identified, and the selected events were analyzed from a synoptic perspective. The results showed that the longest consecutive period simultaneously characterized by heavy intensity and widespread spatial coverage lasted three days, and a total of seven events were identified during the study period. Analysis of atmospheric conditions indicated that these events were primarily associated with the interaction of a surface low-pressure system, a deep mid-tropospheric trough, moisture transport and convergence at the 850-hPa level, and positive cyclonic vorticity at the 700-hPa level. The continuation of this synoptic structure was accompanied by the provision of favorable conditions for ascent, effective moisture transport, and continued precipitation. Topography also played an important role in determining the location and intensity of precipitation cores. Overall, the simultaneous presence of dynamic support and moisture supply was identified as the most important mechanism contributing to the persistence of heavy and widespread precipitation events in the region.