Fall starts today (Sunday) at 3:44PM CDT and it certainly feels like Fall is here with the cool night time temperatures and comfortable days this weekend.
We can thank the trough of low pressure in the jet stream that has carved itself out in the eastern half of the country (see first graphic to the right)
Troughs mean cool temperatures, while ridges of high pressure mean warm temperatures.
Notice how the ridge has warmed temperatures up in the central part of the country (second graphic).
The third graphic shows the GFS model's forecast of the jet stream for late week.
The ridge builds over us, meaning warm temperatures.
By Thursday and Friday we should be back in upper 80s for highs (see 7 Day in 4th graphic).