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Dangerous Heat Expands; Heavy Rainfall Threats; Fire Weather Concerns for the West

The heat will increase and expand across the Central Plains, Mississippi Valley, Southeast and into the Eastern U.S. through the week as high pressure builds across the eastern two-thirds of the country. On the northern periphery of this heat, the threat for severe thunderstorms and heavy rainfall across the northern Plains and upper Midwest through Tuesday. Critical Fire Weather for the west. Read More >

Overview

A major severe weather and flooding event occurred on June 23, 2023 over parts of northeastern Wyoming and western South Dakota. A long-track tornado moved across southern Campbell and Weston Counties, striking the North Antelope Rochelle Coal Mine. Elsewhere, significant flash flooding occurred from Spearfish to Saint Onge, and more widespread flooding occurred across parts of the western South Dakota plains. A few discrete storms produced hail up to 2" in diameter across western South Dakota and northeastern Wyoming. Several strong/damaging wind reports occurred later as the severe thunderstorms moved from western into central South Dakota.

As can be seen in the lightning map to the right (click to enlarge), thunderstorms occurred across essentially all of our forecast area from northeastern Wyoming into south-central South Dakota. Positive cloud-to-ground flashes were especially notable with the tornadic storm that affected the North Antelope Rochelle Coal Mine as well as the Spearfish supercell that produced flash flooding and large hail.

Image
Here is the 24-hour cloud-to-ground lightning map from 6 am MDT Friday (6/23) to 6 am MDT Saturday (6/24). Red plus signs indicate positive polarity flashes and green dashes indicate negative polarity flashes. Total flash counts in upper right.