First things first, let's talk about storm potential on Friday (July 20th). A large storm system is set to move into the Midwest with multiple shortwaves, or areas of energy, diving southeast down the Mississippi River Thursday and Friday. While storms are possible as early as Thursday afternoon, it's Friday's storm potential that raises some eyebrows. As is often the case with severe weather in southern Illinois, it's a conditional risk with plenty of uncertainty. Some forecast guidance suggests high instability and high amounts of shear possible, both would be easily capable of sustaining severe storms. Questions arise with storms late Thursday night into Friday morning and how this impacts the instability, or fuel for storms. The best shear for storms is in the evening, while some of the best timing for instability is earlier in the day. Still a lot of questions, but it's something we're keeping an eye on.
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| Instability Friday Evening |
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| Shear Friday Evening |
Breaks from the heat and humidity have been short-lived through June and July thus far. The pattern has been consistent and stubborn, but FINALLY, a prolonged break is on the way. The stubborn upper-level ridge centered over the Plains and Southeast is set to shift west for the last two weeks of July. It's a pattern shift that signals cool and wet for southern Illinois. The switch to “northwest flow” is not only cool, but active. The concerns of drought as we headed into the Summer are all but gone as this pattern supports continued wet weather with multiple chances for storms. Below, image 1, shows the ridge shifting west while the trough takes hold over the eastern U.S. through the last week of July.
Image 2, is what we call an analog. Analogs look back at similar scenarios and use historical context to indicate what may happen in the future. Through the first few days of August, the image below is a strong signal for the prolonged period of cooler weather on the way.
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| Image 1 |
Image 2
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