Very hot air arrived in Iowa on Wednesday and muggy conditions were not far behind. With surface dew points near 80 degrees in some locations, the lower atmosphere is loaded with moisture. This moisture represents a potential energy source for thunderstorms as condensing water within clouds releases heat which promotes upward motion. The featured map presents a measure of this energy named convective available potential energy (CAPE). CAPE values above 2,000 are often considered significant for severe storms, so do the values shown above 6,000 in Southern Iowa on Thursday evening mean the world is coming to an end? The key word in the CAPE acronym is potential. Just as a watermelon sitting on the top of a sky scraper has a high potential to accelerate if pushed off the edge, the initial push needs to occur. For the atmosphere, weak winds and little convergence of air often means these profiles are left unrealized (nothing to give them a push).

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