South Dakota MCS Eyes 100 MPH Gusts in Hot, Unstable Air — SevereWX

Storms are firing across south-central to southeast South Dakota amid scorching 105-110°F heat, setting the stage for an intense mesoscale convective system (MCS) with damaging wind gusts up to 100 mph.

The SPC's Mesoscale Discussion 1729 highlights a very unstable environment, with modified MLCAPE around 2000 J/kg despite some inhibition. Surface-based thunderstorms are growing on the edge of a cirrus deck tied to a weak shortwave trough, fueled by steep lapse rates, high moisture from the east, and a hot airmass to the west.

Outflow-dominant storms are expected to merge into a cold pool, evolving into a bowing MCS capable of 85-100 mph gusts—potentially warranting a Particularly Dangerous Situation (PDS) watch. Hail up to 1.25 inches is also possible, though wind damage poses the primary threat.

A severe thunderstorm watch is 95% likely within the next 1-2 hours, valid through around 4:45 PM CDT. Keep an eye on areas from roughly I-90 southward into southeast SD.

Stay prepared: Monitor local NWS alerts, secure outdoor items, and have a severe weather plan ready. Avoid travel if warnings issue, and seek shelter away from windows during intense storms.