Stealth Shelf

Though initially inaudible to the ear, this advancing shelf cloud as seen from the parking lot at Noelridge Christian Church in Cedar Rapids, Iowa looked very ominous indeed. The shelf cloud approached from the northwest (upper right), borne upon severe weather in the adjacent counties north and west of Linn County and overrunning the very muggy air present at the time. The gust front produced a mix of high wind, rain and lightning. Top wind gusts were in the 40-50 mph range here, not quite attaining severe levels. Shelf clouds are produced by the cool sinking air from a storm cloud's downdraft. As the cool air mixes with warm moist air, water condenses creating the classic rolling look of the structure. This image, shot at 8:53 PM, Friday, July 22, 2011, looks west.