It's something I might have seen in the past 14 years of computer weather but is quite rare.
Looking at the visible satellite picture below (click for bigger image)- those are thunderstorms that traverse the area spanning those three red dots- which happens to be along the "spine" of North America- the Rocky Mountains.
That's at least 3,000 miles of an almost solid line of thunderstorms- stretching from Dot 1-North- Edmonton- Alberta-Canada region- through Montana, U.S.A. and the Black Hills- through Dot 2 Middle- Denver- Albuquerque- Dot 3 South- El Paso-TX- then into Mexico reaching almost to the Baja Gulf.
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