This is an MCC, an oval-shaped complex of torrential storms known for its extreme amounts of lightning, flash floods, nocturnal nature & very high, cold cloud tops. One occurred lastnight southwest of our area with up to 7" of rainfall in southeast Illinois. Thankfully, it was so droughty & dry in that area that there was less flooding than one would expect. The Little Wabash River is the only river in that area forecast to reach or exceed flood stage & that would be in Clay County, Illinois.
Here, the MCC expanded far enough to the northeast for some rain & thunder & lightning in Fountain & Montgomery counties early this morning.
Sometimes they produce downbursts due to water loading.
They are also known for being so large, they produce expansive areas of clouds (even with their MCV) the next day.
MCCs are especially notable on IR satellite, like the one last night. They look like a massive bomb going off.
They tend to occur in extremely unstable environments of very high dew points (often 80-82) with a lack of shear with some very subtle trigger.
I have seen many times where they form in a pocket of +4000 J/kg ML CAPE where storms pop in that extreme instability with +80 dew points & the surface pressure lowers considerably. They just keep blowing up & expanding with that surface low & feed on the tremendous latent heat energy of such high values of deep layer CAPE.
MCCs are also known for producing gravity waves. These are wave perturbations in the atmosphere that can induce storms downstream in concentric-like waves. As the MCC's massive cloud tops poke through the top of the troposphere or tropopause (like a fish poking its head out of a pond), the ripples extend outward from that area.
Lastnight's MCC shows them well:
Today, this MCC's MCV has brought an extensive area of mid-level altocmulus cloudiness to the viewing area, while the severe storms are firing on the sunnier, more unstable side of the MCV with an outflow boundary.
The gravity waves appear to be promoting some half-circle lines of storms in Tennessee & Kentucky & cloudiness in Ohio to Indiana.
MCC MCV is pivoting away, but as MCV from Wyoming to Nebraska to Kansas to Iowa to Missouri MCS (complex of bowing severe storms) from lastnight & early this morning pivots through south-central Illinois, then Indiana tonight-early Tuesday morning, a few isolated to spotty showers/storms are possible.
The main area of severe, torrential storms with it will stay south of our area tonight-tomorrow morning where Flash Flood Watches are up & SLIGHT RISK of severe weather is found.
Isolated to spotty showers/storms are possible after 12 a.m. through tomorrow morning & midday.
Isolated to spotty activity will be followed by scattered showers/storms afternoon to evening Tuesday.
There is a MARGINAL RISK of severe weather viewing area-wide for isolated severe storms Tuesday.
Muggy to oppressive highs of 85-89 are likely after lows of 67 of 72 in the morning.
There is a trend to shift the storms east & southeast & south of our area Wednesday with just partly cloudy skies & 85-90 here (but still muggy).
For now, I kept it status quo for isolated showers/storms becoming scattered showers & storms for Wednesday PM.
Let's monitor upcoming data to see if this drier trend comes to fruition.
Thursday looks dry with highs 84-89 & also a bit less humid with partly cloudy to mostly sunny skies.
Friday looks hotter with highs 87-93 with increasing humidity & mostly sunny skies (after patchy fog & 60-66 in the morning).
Saturday-Monday looks hot & humid with highs 91-96 with heat indices 97-109. A few isolated to spotty storms may pop daily.
More widespread storms are possible Tuesday/Wednesday of next week with muggy highs 88-94. A couple/few isolated severe storms are possible (MARGINAL RISK parameters seen).
There will likely be a tropical storm or hurricane somewhere in the Gulf of Mexico by mid-next week with a potential late-week landfall in northern Mexico or Texas.
A very brief cool-down is possible at the very end of July.
However, it is looking like hot, oppressive upper ridge may re-establish itself in early August with a "Ring of Fire" pattern north of the area & us seeing intense heat well into the 90s with +100 heat indices.
It appears that a complex of severe storms may impact our area in the "Ring of Fire around August 3 or 4.
Another complex of storms (MCS) may also pass here or just southwest of here August 4 or 5 with a bit of a cool-down here.
There are signs of the hot, oppressive upper ridge returning after this, lasting to mid-August.
Temperatures the rest of July to the first 4 days of August average above normal over a massive area of the Lower 48. The greatest anomalies will occur where they have been continually occurring since June: Midwest to Great Lakes to Northeast to the Canadian provinces of Ontario & Quebec.
The good thing is that we have multiple opportunities for "Ridge Riders" with above normal rainfall. The deep tropical moisture from the landfalling tropical system should wrap around the ridge & add moisture to the "Ridge Riders" on the periphery of the ridge in the Plains.
However, the intense heat of the ridge combined with wetter & wetter soils with lush vegetation mean very high dew points & thus, heat indices reaching dangerous levels.
We may not have seen the most oppressive day or the highest heat indices or actual air temperatures of 2020 just yet.
Mid-August period will shift to a cooler, more comfortable regime here & the storms will tend to shut off.
Temperatures average normal in mid-August.
Rainfall averages below normal.
Latter August looks warmer than normal, but not to the degree of early August.
Latter August is trending drier than normal unless a tropical system remnants make it up into our area.