Hiker dies after being struck by lightning in Utah
5-minute CONUS Sector GOES-18 (GOES-West) Visible and Infrared Window images (above) showed the rapid development of a relatively compact thunderstorm east-southeast of Salt Lake City on 18 July 2026.
The coldest thunderstorm cloud-top infrared brightness temperature was -48.76 C at 1741 UTC (above) — which represented an altitude just below the Most Unstable (MU) air parcel’s Equilibrium Level (EL), according to a plot of 1800 UTC rawinsonde data from Salt Lake City (below).
This thunderstorm produced GOES-18 GLM-detected lightning activity from 1726-1816 UTC (below) — beginning 5 minutes after the LightningCast probability first exceeded 75% (violet contours), and 10 minutes after the probability first exceeded 50% (green contours). The parallax-adjusted LightningCast product was used in this case, to portray the highest probability of lightning at the surface (instead of at the cloud top). Tragically, a hiker died after being struck by lightning near American Fork Twin Peaks (which is located about 4 miles southwest of Alta). (media report)
A time series of GOES-18 LightningCast probability and GLM flash counts in the vicinity of Heber City Municipal Airport (KHCR) — the closest airport to the fatal lightning event — is shown below. In addition, at 1756 UTC lightning in the distance was noted at Salt Lake City (KSLC) and Provo (KPVU).
The largest GOES-18 GLM Flash Point area in the vicinity of Alta was 228 km2 at 1806 UTC (below). Note that the Flash Point appeared just south of the cluster of large Flash Extent Density pixels — this is because gridded GLM products (such as Flash Extent Density) are mapped to correspond to a mean cloud top height, in contrast to the Flash Points which are mapped to correspond to the surface location of the lightning.
