Analysis of the surface distribution of precipitation associated with intense extratropical cyclones reveals elongated maxima aligned with the steering flow. Rapidly intensifying cyclones create precipitation maxima which are better defined and contain more moisture than weaker cyclones. The distribuitons are associated with the formation of a precipitaiton generating zone (PGZ) aligned with the midtropospheric jet ahead of and parallel to the surface cold front extending southward from the surface low. These zones tend to move along their axes and are host to the most frequent and intense convective activity in the extratropical cyclone. Hourly rain gage measurements at sites in their path indicate an average of three precipitation peaks in 16 storms studied, although radar echoes disclose that many mesoscale structures with high reflectivity are simultaneously active. It is hypothesized that formation of such zones is most pronounced when momentum transport out of the jet increases the advection of warm moist air at low levels, thereby sustaining or increasing convective instability. In this context, the PGZ becomes the dominant feature of the extratropical cyclone and is crucial to intensification. ¿ American Geophysical Union 1990