Stepping out the door early Tuesday was certainly a pleasant experience, one I would equate more with fall than late summer. That wall of humidity that's so common at this time of year was nowhere to be seen and temperatures in the 50s were a subtle (but gentle) reminder that we're on the down-side of the warm season. It's no wonder when you see a trough like this digging into the Midwest. That's a few weeks ahead of schedule.
I couldn't help but be impressed with the 90kt jet max that was streaking through NW Iowa.
Another sign of fall was the big surface high over the northern Rockies that is building southeast. That will keep things pleasant right on through Wednesday.
In fact, Wednesday will get off to a crisp start with lows that have a good chance of reaching the 40s. The NAM has this for early morning readings. Wednesday afternoon however looks perfect, sunny and comfortable.
Thursday will be a bounce back day as return flow sets up southerly winds and warmer temperatures. Highs in most spots have a chance of reaching the low 80s, maybe even the mid 80s south of I-80. Later in the day a t/storm is possible over the far south as a fast moving cold front plows across the region. Thus, the summery temperatures won't last long as winds back to the north Thursday night sending another tentacle of cool air back into the region to close out the week.
After that Labor Day weekend starts shaky with the aforementioned front stalling over Missouri. North of it cool dry air is in place with dew points deep into the 50s. Further south it's a different story with readings hovering near 70.
Water vapor in the form of PWATs really pools over my region. The EURO has values over 1.60" as far north as Cedar Rapids, Iowa Saturday evening.
That's more than an inch above the seasonal norms.
The EURO gets the rain train rolling late Friday night and Saturday. That said, an important trend late Tuesday is a southward shift in the heaviest rains on that model. The latest runs keep it south of I-80 where the previous runs had it north of that benchmark.
The GFS remains further south and lighter on precipitation totals.
So this is the low confidence part of the forecast. Where that front sets up and how strong the low level jet gets cranking will determine just how wet and cool Saturday turns out to be in any given area of the central Midwest. No matter where the heaviest rain falls, an east wind looks likely and an east wind is an ill wind. The EURO shows gusts to 20 mph during the afternoon.
With low clouds and the threat of precipitation, the potential is there for a dreary and very cool day. Certainly well below normal with the coolest areas struggling to get much above 60.
As it stands now the GFS seems a bit dry in my opinion and the EURO might be a bit wet. However, considering the parameters and overall potential, I am leaning more towards what the EURO is showing. The Weather Prediction Center is too showing this for rainfall through Saturday night. I think this is still a bit high and should be shifted south by about 100 miles.
Still some time to figure this out but if you have outdoor plans for the start of your holiday weekend be advised there are issues on the table, especially Saturday. Roll weather...TS