GLM Extent Density of Lightning is the number of lightning flashes that occur within a grid cell over a given period of time, and was the first GLM product routinely available to NWS forecasters. Many years of research and operational lightning mapping array demonstrations have shown FED to be the preferred total lightning product. FED best portrays, in a single product, the quantity of GLM flashes (storm trending applications) and extent of GLM events (depicting lightning areal coverage). Additional gridded GLM products are under evaluation for future deployment.