It’s been a day dominated by heat and now isolated thunderstorms are forming from Brookings to Pierre and Rapid City. These are pivoting out of North Dakota but much of this will never reach the ground.
A Heat Advisory lasts through 7:00 p.m. this evening and covers much of central and eastern KELOLAND. Some of the warmest areas (Badlands) are not included in the Advisory but will be scorching, nonetheless. Our limited shower activity will continue through evening before a weak cold front crosses over from North Dakota tomorrow morning. The ENE winds behind that will drop highs tomorrow by 5-10° but it’ll still be a hot start to the weekend. There’s also a decent chance of rainfall by tomorrow afternoon and evening. That is initially confined to the NW corner of South Dakota but could spread east and south by evening. Some of these storms could turn marginally severe, though a NE wind is usually a storm killer. If the front stalls out in western South Dakota, the storm chance goes up a good deal.
By Sunday, most will be dry. Scattered pockets of rain look to form near Aberdeen and Rapid City. Aberdeen continues to be on the northern edge of the heat ridge; until that breaks, weak systems bring slight chances of rain to the northern tier for the next few days. In the seven-day forecast, Aberdeen has many more shots of rain than Sioux Falls.
Monday looks to be another hot day. Highs will be roughly 15° above their September average. We do expect another shot of cool-er air to arrive on Tuesday, along with a broken line of storms. Highs become more manageable by week’s end, though still a little bit above average.