You've got storms moving through right now and into the early morning hours. The first batch is already rolling northeast along a cold front that's draped right across Sioux Falls. Expect that initial line to clear out around 11 pm, but don't relax yet—a second, stronger wave of storms is coming in after midnight and should be the bigger threat in our area. This second round looks to hit hardest between about 1 am and 4 am Wednesday morning, with damaging wind gusts near 80 mph, large hail, and heavy rain on the table. Once that clears by mid-morning Wednesday, Tuesday itself will be gorgeous: sunny and hot, hitting 91 degrees with hardly any rain chance. Then we're right back into it Tuesday night as the pattern stays unsettled.
What's driving all this activity is an upper-level jet stream, that river of fast air around 30,000 feet, that's been positioned to keep waves of low pressure rolling through the region. The atmosphere right now is unstable (that CAPE value around 3000 joules per kilogram tells us there's plenty of energy for storm development), and we've got wind shear, the change in wind direction and speed with height, that favors organized, rotating storms. The Low Level Jet (LLJ), a corridor of especially fast wind closer to the ground, is ramping up overnight and will be the real engine behind the stronger second round. That combination of instability, shear, and a strengthening LLJ is what meteorologists watch for when we're worried about severe weather with strong winds and hail.
The active pattern sticks around all week. Wednesday itself looks to have scattered storms with better chances northwest of us in Iowa, but Thursday into Thursday night another well-defined wave moves through and will bring another round of heavy rain and severe weather threats. By the weekend, the upper-level flow shifts a bit more westerly, which usually weakens the setup, but expect near-daily chances for storms through at least Thursday. This is the kind of week where your phone's weather alerts will be working overtime.