NWS Huntsville is providing Impact-Based Decision Support Services (IDSS) to protect life and property at an outdoor sporting competition in the Decatur, Alabama area this week. A decaying Mesoscale Convective System (MCS) moved across north Alabama this afternoon, forcing a delay in the competition for several hours. While the North Alabama Lightning Mapping Array (NALMA) helped determine what to tell local emergency managers about the start of the lightning threat, the NALMA really shined in trying to figure out when the lightning threat would end.
The example images include NALMA Flash Extent Density data, which are represented by irregular pink and purple shapes displayed over the KGWX radar reflectivity. Both the 1949 and 2007 UTC indicate scattered very low flash rates extending over a broad area–including the Decatur area–suggesting occasional in-cloud flashes within the trailing stratiform region of the MCS. This is a known threat with MCSs, but it was not clear at the time how long the lightning threat would persist. Use of total lightning information from NALMA enabled NWS Huntsville staff to determine that the lightning threat would not subside until rain subsided.
With the launch of GOES-R and the Geostationary Lightning Mapper, these kinds of data will improve lightning-based IDSS across a much wider cross section of the CONUS.