Here’s a closer look at Tuesday’s storms. At noon, there was just a little activity near Dell Rapids and in SW Minnesota. We see here, the first outflow boundary.
By 1 p.m, that outflow sparked up a more storms centered on Sioux Falls.
By 2 p.m., McCook County had most of the activity but there were other storms in NW Iowa and around Hutchinson County.
By 3 p.m., there was a good amount of stormy activity on either side of I-90.
Here’s another look at how it happened.
It all started with that first storm; there was just enough instability in the atmosphere to get it going. But the atmosphere wasn’t set up to keep it going so it died out, causing all the energy and wind in the storm to fall out and spread out in all directions.
And the edge of that is called the outflow boundary and it acts like a mini cold front, which can trigger more storms if the atmosphere is ready, which is what happened to Sioux Falls.
Then that intense storm over Sioux Falls died out and sent out its own outflow boundary and that traveled through Turner County. But the atmosphere wasn’t ready for storms, so the boundary moved through quiet and stabilized the air. So little rain fell.
So if you got little to no rain, you’re not alone and were probably just hit with an outflow boundary before the atmosphere was ready for storms.