Highs today reached 86-92 after lows of 68-73.
However, dew points peaked at 75-80, resulting in heat indices peaking at 95-106 today.
Multiple outflow boundary from earlier storms are laid up over the area. This, with subtle MCV near Chicago, is making for additional scattered, slow-moving, pulsey storms. There is still the risk of briefly severe storm, even into tonight with oppressive, sultry airmass around.
Local heavy rainfall with flash flooding is possible.
The storms on radar are pretty much stationary & will tend to ridge outflow boundaries north or south & rain themselves out while new storms form nearby.
Torrential storms should form in Missouri & Illinois into an MCC (complex of flooding storms with oval shape on IR satellite with cold, cold cloud tops) with up to 6" of rainfall overnight through Tuesday morning. This MCC should form well-pronounced MCV that will serve as a trigger for scattered storms here tomorrow.
There is the risk of a couple isolated severe storms & risk of locally-heavy rainfall that may produce flash flooding.
Our highs will run 86-91 tomorrow, but dew points of 75-81 will make it feel more like 97-106.
MCV may produce MCC over Illinois that will merge with MCC/MCS over Iowa & Minnesota Tuesday night-early Wednesday morning.
MCS is large, organized complex of storms with severe weather often on the front of them as a large squall line or bow, followed by a large area of stratiform rain. An MCC differs in being more of just a large mass of torrential storms with big flooding threat. As said before, they show up on an IR satellite with extremely cold cloud tops & are usually perfectly symmetrical.
Regardless, big flash flooding situation is setting up from Iowa & Minnesota to Illinois with +6" of rainfall possible in places & some isolated severe weather risk. It will be an all-out light show of extreme lightning from Minnesota to Illinois as 80-degree dew points & highly-unstable air fuel the storms.
This means two things for us:
1. Outflow boundary from MCC & MCS & the MCV will bring scattered storms Wednesday.
2. The very wet soils southwest, west, & south of us will lead to tremendous moisture being evaporated into the air there & around the region. This very humid air will combine with the heat to lead to dangerous heat indices late this week & right through the July 4th weekend.
Think of it as sticking wet clothes in a hot dryer & the tremendous steam that comes of those clothes as they dry. Your dryer window fogs up!
Considerable upper ridging & capping will tend to limit storm development Thursday through Tuesday.
However, given how intense the heat & instability will be, I do think a few storms may occur randomly. However, I would like to wait to see which day has the best potential of a few pops before I put say 20% or 25% or 30% on any day.
Count on a long period of intense, oppressive heat.
July looks overall hotter & actually overall drier than normal.