It is hot and humid once again and showers and thunderstorms are developing ahead of a cold front. Temperatures are well into the 80s and 90s...
Back into the Dakotas "cooler" air has started to move in behind this front. But out ahead of it there is a lot of moisture and instability. CAPE (convective available potential energy), which measures instability, is very, very high this afternoon. 1,000 to 2,000 is enough for thunderstorms to get going. Because of the incredibly hot temperatures, CAPE values of 4,000 to 6,000 were not uncommon Saturday afternoon -
And so a Severe Thunderstorms Watch has been posted for portions of Iowa, Nebraska, Minnesota and Wisconsin.
This Watch my be extended further south and east depending on the strength of the line of storms through the evening. Here's a look at the hi-resolution rapid refresh model (HRRR), which runs every single hour -
These storms will mainly pack a punch with strong winds and heavy rain through this evening. Some small hail will be possible and an isolated tornado is also possible out in western Iowa with any discrete thunderstorms. The storms should move into eastern Iowa and Illinois as a line, with wind as a primary threat.