ND/SD Border High-Based Supercells Eye 90 MPH Gusts, 3.5-Inch Hail Cores — SevereWX

ND/SD Border High-Based Supercells Eye 90 MPH Gusts, 3.5-Inch Hail Cores

Storms are firing up along the southern North Dakota and northern South Dakota border, with SPC's Mesoscale Discussion 1663 highlighting a serious severe weather setup this evening. As of 2050 UTC, isolated thunderstorms have already popped in Perkins and Meade Counties, SD, amid a growing cumulus field in far southwestern ND and northwestern SD.

A southeastward-moving cold front is fueling more development, supported by steep low- and mid-level lapse rates, 30 knots of effective shear, and straight hodographs from a modified BIS sounding. Upper-level flow is strengthening, setting the stage for high-based splitting supercells that could produce large hail—most probable 2-3.5 inches—and severe outflow winds to 75-90 mph, with some gusts potentially exceeding 80 mph.

These initial supercells should transition into clusters as they spread eastward, driven by efficient evaporative cooling and cold pool growth. The primary threats will shift toward damaging wind gusts, but don't count out those hefty hail cores early on.

SPC pegs the odds of a Severe Thunderstorm Watch at 80% later this afternoon, covering portions of southern ND into northern SD (LAT...LON blocks outline the polygon from roughly 45-47N, 100-103W).

Most probable peaks: 75-90 mph winds, 2-3.5 inch hail.

Keep an eye on radar—activity peaks through 2300Z.

Preparedness: Review your severe weather plan, secure outdoor items, and monitor local NWS updates or apps like SevereWX.net for real-time intel. Stay safe out there.