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The National Weather Service says a powerful lightning strike combined with unique atmospheric conditions caused Friday night’s widespread loud boom and bright flash across Northern Virginia.
The phenomenon, which was reported across a wide area stretching from Gainesville to Leesburg and beyond, brought dozens of inquiries to the NWS Sterling forecast office this weekend.
The loud clap of thunder was the result of a lightning strike that occurred in southern Frederick County, Maryland, just before 10:50 p.m. Friday, the weather services said in a social media post.
“The resultant thunder shook the windows at our office here in Sterling near Dulles Airport, as well,” forecasters wrote.
The exceptional noise was attributed to two main factors: the nature of the lightning and a natural “echo chamber” effect.
First, the strike was identified as a positive cloud-to-ground lightning strike. This type of strike originates from the top of a thunderstorm rather than the base and carries “a lot more power than usual,” the NWS said.
Second, a temperature inversion was present near the ground. Typically, air cools with height, but this inversion meant air a few hundred to a couple thousand feet above the ground was actually warmer than the air at the surface.
“While not rare (they actually happen most nights), that inversion creates a barrier that sound ‘bounces’ off of, so it acts like an echo chamber – making an already powerful and loud strike seem even louder!” the NWS wrote.
For more information on the science behind the sound of thunder, go to noaa.gov/jetstream/lightning/sound-of-thunder.
