The National Weather Service Storm Prediction Center plans to issue a “particularly dangerous situation (PDS) severe thunderstorm watch” for the northern third of Indiana by 6 p.m. EDT, according to a mesoscale discussion the SPC issued at 4:38 p.m. EDT.

The SPC issues PDS severe thunderstorm watches when there is a threat of a high-end “derecho” with widespread wind damage.

 According to the mesoscale discussion, thunderstorms developing across northeastern Iowa, southern Wisconsin and northwestern Illinois will congeal into an accelerating convective system and move east-southeastward across northern Indiana during the late afternoon and evening hours. Damaging winds, some in excess of 65 knots, (74.8 mph) are likely, along with embedded tornadoes.