Heavy Rainfall in the Southwest and Southeast This Weekend; Monitoring Tropical Cyclone Formation Which Could Impact the Southeast U.S.

Heavy rainfall from monsoon thunderstorms may bring isolated flash and urban flooding to the Desert Southwest. A near-stationary front will bring numerous showers and thunderstorms to much of the Mid-Atlantic and Southeast. Tropical wave (AL94) is likely to become a depression. Significant uncertainty remains in the track and intensity, but chances for impacts to the Southeast are increasing. Read More >

Background

The lightning images below are updated daily around 7:30–8:30 AM and contain 24-h accumulations of lightning ending at 6 am MDT (5 am MST) each day. There are two sets of images for (1) NLDN cloud-to-ground flashes only and (2) GOES-East Lightning Mapper (GLM) cloud flash points. Option #1 only represents cloud-to-ground lightning flashes, and is based on a surface detection network. Option #2 does not discriminate between cloud-to-ground versus in-cloud flashes (i.e., it represents the total lightning) and is based on satellite. In-cloud lightning flashes can comprise 60–90% of the total lightning (i.e., most lightning does not reach the ground). Satellite-based lightning detection also does not depict the exact location where the flash occurred because of an issue known as "parallax." Mouse over each day to view the 24-h cumulative lightning flash maps. Printable versions are at the bottom of each of the three map segments.