Is Summer Weather Over Already? Not Quite

Another big trough has positioned itself across the middle of the country bringing unseasonably cool air. While cooler than normal conditions will stick around for the remainder of the week, the core of cool air that at times made it south of the Hudson Bay this summer can be seen much further north this time around. Ultimately, that means the southerly flow will be able to return a bit quicker.

500mb chart Wednesday morning showing large trough over eastern U.S., large ridge in western U.S.

By late week, the upper level northwest flow will moderate and almost become zonal while low level south/southwest flow sets up. Low level south/southwest flow will bring an increase in temperatures and an increase in humidity and moisture. While temperatures Wednesday afternoon top off around 80˚, by Friday temperatures will be warming back into the upper 80's, a direct result of the low level south/southwest flow.

Friday evening 850mb map. The south/southwest flow can be identified easily setting up over the Plains/Midwest.

While models are in agreement of the return low level flow, models start to disagree when handling the modest upper level flow. An upper level low can be found on both the GFS and Euro by Sunday morning making it's way across the lower Missouri Valley. The differences arrive with the GFS tracking the low through much faster than the Euro. The GFS solution would track potentially heavy rain across the lower Ohio Valley Sunday (seen below). 

GFS Sunday morning. Result of upper level shortwave moving across the middle of the country. 

The Euro is much slower with the progression of the low, keeping the heaviest rain to the west throughout Sunday and bringing lesser amounts Monday and Tuesday as the low slowly moves east.

Euro Sunday evening. Low still hasn't tracked as far east as GFS shows Sunday morning.

5 days out, pinpointing which model has a better handle on the late weekend storm system is nearly impossible. As the week rolls on and we draw closer to the weekend, models are likely to come in better agreement, which maybe somewhere in-between the current outputs from the GFS and Euro.

Last thought for the day: The long-range charts in the GFS show a large upper level ridge building across the eastern two thirds of the country later this month. This pattern is more seasonable for late summer and would result in above temperatures towards the end of August. 

Wednesday August 26th 500mb map

Those are some of the things we'll be watching over the next week or so. As always, thanks for reading.

-Nick