Cap should pop off in explosive environment from southeastern Missouri to Kentucky & Tennessee this evening. These supercells will eventually congeal into a line that may become an all-out widespread damaging wind event (derecho?) that reaches nearly or to the Gulf Coast by early tomorrow morning.
This is a May-style event!
Very hot, dry air from the now downright historic southern Plains heat wave has slid over this area today & kept a lid on like a boiling pot. As the sun sets, lid should be removed as upper low drifts southeastward, cooling that hot, dry layer & effectively removing the cap.
Already with the afternoon outbreak, baseball hail fell in the Louisville, Kentucky area & several apparent tornadoes occurred in northern & eastern Indiana (as well as straight-line wind damage).
I only received three reports of wind damage in our area. Power lines down southwest of Rochester & south & northeast of Kokomo (with tree & limbs down too northeast of Greentown). Some pockets in Howard County received 2.4" of rainfall & up to 2" fell in Fulton County.
Here, we will enter a lull for much of tonight for any rainfall. Just clouds will pivot through. Some showers will begin to pivot in tomorrow morning. Lows will run in the mid 60s.
A scattered of showers & t'showers will increase tomorrow with daytime heating with lots of clouds & some sun. With rather breezy conditions, highs will only reach 74-78. Rainfall coverage should peak at 60% in the late afternoon.
Some more scattered showers & t'showers will bubble Sunday, especially in the afternoon. Rainfall coverage should peak at 45% in the afternoon. Highs will run 75-80. Lows Sunday morning will run near 60 to the lower 60s.
Even Monday, we should bubble up a few scattered showers & t'showers with the daytime heating with sun & clouds. Highs should run 79-83 after lows of 58-62 in the morning.
Tuesday & Wednesday look dry with temperatures warming up, but humidity remaining pretty low. Tuesday should run 82-86 & Wednesday 84-89. Lows will be in the 60s.
A surface cold front should pass Thursday morning to around midday. A highly-broken line of showers & t'showers may form along it as higher humidity pools ahead of it. The humidity will tend to fall in the afternoon with the passage of the front, however. Highs will run 80-87 north to south in the viewing area as southwesterly winds turn to the north with that front coming through. Cooler & comfortable air will come in behind it for Friday.
Notice how the intense Southern Plains & Lower Mississippi heatwave will continue & first contract, then expand again (pink & purple color = intense heat near & +100 actual air temperature).
Meanwhile, notice how we actually see that cool-down next Friday-Sunday, July 29. Temperatures look consistently below normal (normal: 85/64).
My continued thinking is that between the intense heat wave & our cooler weather will be the "Ring of Fire". Multiple clusters & complexes of storms (some severe) will develop & pass in a zone from Nebraska & Kansas, through Missouri to western Tennessee. Heavy, flooding rainfall may occur in some of these areas at times. I am still siding with below normal rainfall here, unless that "Ring of Fire" expands northeastward some. We will monitor.
This is a July 20-30 rainfall total graphic for the ECMWF model. The mapping & model template are courtey of Dr. Ryan Maue.
Notice how the intense heat wave remains pretty contained & even wanes a bit getting to the first day or two of August. However, notice in the last frame (August 5) how the intense heat suddenly expands north to the Dakotas & then east to Virginia with widespread 90s to lower 100s.
This is our developing brief lobe of heat wave flirtation. This lobe should expand over our area with burst expect near mid-August. A couple of days may be 90-94 with high humidity blowing off of the wet ground well to our southwest. This may only last a couple of days, but heat indices may run 99-107 with overnight lows in the uncomfortable 70s.
Notice this sudden, rapid expand of the hot upper ridge with cluster of severe storms in a "Ring of Fire" like occurring on its periphery from Montana to Ontario in those upper jet streaks (in green to dark yellow color).
However, notice as quickly as it quickly expands to the north & northeast, it flattens, then a trough develops in our area. This means cooler weather returning here.
So, another rather strong cold front may put the kabosh on this brief spurt of heat, knocking temperature back below normal. There will likely be storms with this front.
You can see an upper jet streak cross the area with potentially +2500 J/kg possible with that heat & humidity. This could be the next organized severe weather scenario. Again, this would be near/at mid-August.
Notice another jet streak & trough near August 21/22 in the trough. This will need to be monitored. It does not exceptionally hot during this time, but the return of high humidity with 80s.
Still thinking a heat wave may round out the end of meteorological summer in late August (after 24th) to near Labor Day with 95-99 & heat indices 100-107.
It may come to an abrupt near around/on Labor Day with cooler weather arriving with a cold front.