A Climatological and Keyword-Based Analysis of National Weather Service Mesoscale Precipitation Discussions

Flooding is one of the most hazardous weather-related phenomena in the United States, with flash flooding being a particularly dangerous form of flooding generally caused by short-duration, high-intensity precipitation. In April 2013 the National Weather Service (NWS) Weather Prediction Center introduced the Mesoscale Precipitation Discussion (MPD) product to address the forecast challenges associated with these events across the lower 48 states. This study evaluates the frequency, spatial distribution, and storm types associated with short-term forecasts of potential flash flood events through the lens of an MPD catalog for a period between 2013 and 2023. The spatial and temporal distribution of MPDs illustrates the likely storm types that most frequently produce short-duration, high-intensity precipitation over CONUS including atmospheric rivers (ARs), convective storms, fronts, and monsoons. Analysis of MPDs with AR keywords shows the highest frequencies in the western United States, whereas analysis of MPDs associated in space and time with AR features in AR detection tools (i.e., tARget, AR Scale) shows much higher frequencies over the southeastern United States. These results suggest that AR-related forecast diagnostics and the environments they describe may be useful for ingredients-based operational forecasting of flash flood conditions for various storm event types in locations beyond the West Coast of the United States. Additionally, this study highlights the ingredients-based forecasting methodology, supports the recent efforts by the NWS to quantify skill of the MPD product, and contributes to the objectives of NOAA’s Precipitation Prediction Grand Challenge.