Our stretch of epic win in the weather department continues into the weekend despite a few showers that could be around tomorrow afternoon and evening. I think we can all deal with that.
After the weekend, unsettled weather takes hold for a couple days as a disturbance pushes northeast out in front of a deepening trough that sets up shop across the Midwest and gradually marches east. This trough will bring a more pronounced taste of Fall to the Midwest and Great Lakes next week.
There's pretty good consensus between the GFS and Euro that the core of cool will be over the Great Lakes and Midwest as the trough's core sets up shop over them. We will get glancing, but noticeable shots of cool that begin Tuesday night/Wednesday (see more below in a moment) and get reinforced in varying capacity next weekend as a second storm system may fire through late next week or at the beginning of next weekend. The core of cool varies in intensity between the models -- specifics of "how cool" aren't necessarily important this far out -- but the agreement in the worst of cool being in the Midwest as we get through the latter half of next week are in solid agreement.
For us, the first system (early next week) could bring a solid rain event Monday into Tuesday before the front clears the coast late Tuesday night or early Wednesday, bringing the first shot of cool. For those who like seeing "cold" 850 numbers on computer modeling, here's a nice treat for you as you can see the freezing line at 5000' is drifting back into the US. The blue "0" line is freezing at around 5000' up, with temperatures aloft dropping quickly and a cool core of high pressure pushing into the Ohio Valley, the potential for some frost in parts of the Midwest and Great Lakes exists as we get into Tuesday night and Wednesday night, with the best chances of this occurring in Michigan and perhaps Northwest Ohio and Northern Indiana. Our coolest nights would be Wednesday & Thursday nights, but frost locally is not likely...although lows in the 40's outside of the city will be pretty likely on either or both of those nights.
Computer modeling suggests that this cool regime would continue into next weekend (the 22nd/23rd) and perhaps the final week of September as the trough holds serve across the Lakes and Northeast.