Southern Dakotas High-Based Storms Charge Toward 90 MPH Winds, 3-Inch Hail Clusters — SevereWX

Southern Dakotas High-Based Storms Charge Toward 90 MPH Winds, 3-Inch Hail Clusters

A batch of high-based thunderstorms is rapidly organizing across the southern North Dakota and northern South Dakota border this afternoon, per SPC Mesoscale Discussion 1663. What started as a cumulus field in far southwestern ND and northwestern SD is now producing isolated storms in Perkins and Meade Counties, SD, with more growth expected along a southeastward-moving cold front.

Steep lapse rates, 30 kts of effective shear, and elongating hodographs from strengthening upper-level flow are fueling initial splitting supercells. These could drop large hail up to 2-3.5 inches—think golf balls or bigger—and damaging straight-line winds to 80+ mph. As the evening progresses, evaporative cooling will sharpen a cold pool, driving upscale growth into clusters where 75-90 mph gusts become the main danger.

SPC pegs Severe Thunderstorm Watch odds at 80% through 2300Z (5 PM CDT). Storms will push eastward, so residents from Bismarck to Aberdeen should monitor radar closely.

Peak Threats:

Keep NOAA Weather Radio on, have a severe weather plan ready, and shelter indoors away from windows if storms approach. Check SPC's site for updates.