This blog is a follow-up to a piece that I wrote about yesterday about severe weather potential in the Upper Midwest. You can find that blog here: https://www.dtnpf.com/…
The setup was good for severe weather yesterday. A cold front was moving through the Northern Plains on the morning of July 28 and was expected to ignite thunderstorms in northern Minnesota and northwest Wisconsin in the afternoon and evening.
Those storms were forecast to move southeast along a stalled frontal boundary across Wisconsin in the evening and overnight hours. Daytime temperatures in the 90s Fahrenheit and dew points well into the 70s Fahrenheit provided ample fuel for thunderstorms to grow rapidly. And strong winds aloft were likely to push the thunderstorms along and aid in developing a "rear-inflow" jet, a way for storms to focus and prolong strong winds.
All of these ingredients combined together prompted the Storm Prediction Center (SPC) to issue a rare "Moderate Risk" of severe weather across much of Wisconsin into southwest Michigan. In their discussion, they used the term derecho, which should have sparked fears about the damage that was caused in Iowa through Indiana on Aug. 10, 2020.
Things were going mostly to plan Wednesday afternoon. Heat was building, moisture was increasing, and the frontal boundaries were in place.
Just after 7 p.m. CDT, storms flared in the exact spots that models were predicting earlier in the day, though a tad late. They grew rapidly and were quickly warned for potentially severe hail and wind gusts. A few of the storms saw enough rotation to warrant tornado warnings in western Wisconsin. The storms quickly developed bows on the front end of the storms and the damage paths were set across Wisconsin.
The western flank of the storms took a slightly more southerly path however, and moved into northern Illinois while another went across Lake Michigan into northern Indiana and southwest Michigan and diminished as it moved away from the lake into more stable air Thursday morning.
Whether it was due to the western flank eating some of the energy for the main core of storms or that the winds did not line up just perfectly, severe wind gusts did not reach hurricane-force save for one report in central Wisconsin early in the storm history.
Regardless of the derecho classification, the storms did produce some heavy damage across a long path through the Midwest. Many wind gusts of 60-70 miles per hour were reported along the storm paths. It remains to be seen whether or not there was widespread crop damage. But for certain there will be some. This may not have been a derecho by definition, but the damage that occurred could have had a large impact for some producers hoping for good yields.
John Baranick can be reached at email@example.com
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