This paper presents an ingredients-based approach to forecasting flash flood-producing storms. The key idea is that heavy precipitation, which can lead to flash floods, results from sustained high rainfall rates. High rainfall rates depend on the rapid ascent of moist air, the amount of water vapor in the air, and the efficiency of precipitation. The duration of a storm is related to the speed and size of the system. The paper discusses the meteorological processes that bring these ingredients together, primarily in midlatitudes, and how they apply to tropical systems. It also provides three case examples to illustrate the methodology. The paper emphasizes the importance of identifying which ingredients are critical in any given situation, as this helps forecasters anticipate heavy precipitation events. The paper also discusses the challenges of forecasting flash floods, including the difficulty of predicting the magnitude of an event and the interaction between meteorology and hydrology. The paper concludes that an ingredients-based approach can be improved through advances in scientific understanding and technological tools, but the basis itself should remain essentially unchanged. The paper also discusses the different types of storm systems that can produce flash floods, including convective systems, mesoscale convective systems, and nonconvective precipitation systems. The paper emphasizes the importance of understanding the meteorological processes that contribute to flash flood events and the need for forecasters to recognize the potential for heavy precipitation in a timely manner.This paper presents an ingredients-based approach to forecasting flash flood-producing storms. The key idea is that heavy precipitation, which can lead to flash floods, results from sustained high rainfall rates. High rainfall rates depend on the rapid ascent of moist air, the amount of water vapor in the air, and the efficiency of precipitation. The duration of a storm is related to the speed and size of the system. The paper discusses the meteorological processes that bring these ingredients together, primarily in midlatitudes, and how they apply to tropical systems. It also provides three case examples to illustrate the methodology. The paper emphasizes the importance of identifying which ingredients are critical in any given situation, as this helps forecasters anticipate heavy precipitation events. The paper also discusses the challenges of forecasting flash floods, including the difficulty of predicting the magnitude of an event and the interaction between meteorology and hydrology. The paper concludes that an ingredients-based approach can be improved through advances in scientific understanding and technological tools, but the basis itself should remain essentially unchanged. The paper also discusses the different types of storm systems that can produce flash floods, including convective systems, mesoscale convective systems, and nonconvective precipitation systems. The paper emphasizes the importance of understanding the meteorological processes that contribute to flash flood events and the need for forecasters to recognize the potential for heavy precipitation in a timely manner.