118
FXUS63 KILX 151758
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1258 PM CDT Sat Aug 15 2026

.KEY MESSAGES...

- There is flash flooding ongoing across portions of central
  Illinois this morning, where thunderstorms track over areas
  that have already seen 4-6 inches of rain since Thursday.
  Areas north of a Havana to Bloomington line are most at risk.

- Storms have the potential to produce damaging winds today and
  tomorrow. SPC has a marginal (level 1 of 5) risk of severe
  weather for the weekend.

- The heat and humidity remain a concern for the weekend, with
  the hottest conditions in the southern half of the state.

&&

.DISCUSSION...
Issued at 220 AM CDT Sat Aug 15 2026

Tonight, storms are moving across central IL. There is a low risk
(but non-zero) for damaging winds within these storms, but the main
concern is the flash flooding risk. WPC has areas near and north of
I-72 in a moderate risk (level 3 of 4) for excessive rainfall for
the overnight hours. The 00z sounding shows the environment having
PWATs of 2.2-2.4 inches. Over the last few days, this area has
gotten 3-6 inches of rain, with some locally higher amounts. The
storms passing through tonight are expected to drop another 2-5
inches with the LPMM suggesting some localized pockets of up to 10
inches. Flash flood guidance seems a bit generous (too high). If the
pockets of higher rain set up over where the ground is already
extremely saturated, flash flooding is likely.

For the remainder of the day after this morning round of convection
exits about 15-16z, there is a marginal risk for severe weather for
additional activity that will move through. It will be very similar
to what has happened over the last few days. The next round of MCS
activity will move into central IL by late evening and will continue
into the overnight hours. The main concern will be damaging winds
and the heavy rain potential.

There is another marginal risk for severe weather again tomorrow for
areas south of a Schuyler to McLean County line with a similar
environment in place as previous days. The forecast will continue to
evolve as we get newer runs of the models.

Temperatures remain hot and humid. The heat advisory for south of I-
70 is valid through Sunday. Heat indices of 100-110 degrees are
forecast through Sunday, but how far north these heat indices get
will depend solely on the convection location. Like yesterday for
example, the convection lingered further south longer than forecast,
so heat indices struggled to hit triple digits.

Next week may bring us a brief break in the active weather and the
heat briefly. A high pressure area will set up over the Upper
Mississippi Valley / Great Lakes region by Monday, behind a cold
front that will move through central IL during the day. Temperatures
starting Monday into much of the next week will be mainly in the
upper 70s to 80s for highs and 60s to low 70s for lows.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1258 PM CDT Sat Aug 15 2026

Mostly VFR conditions can be expected until 06Z although some
brief IFR-MVFR cigs are possible at KPIA the first few hours.
Another cluster or two of thunderstorms is expected to impact
the area overnight as a cold front approaches from the NW, with
brief MVFR cigs/vsbys possible in storms. Have a tempo group
for thunderstorms at each site during 06Z-12Z timeframe.
Guidance points to widespread MVFR cigs following these storms
at KPIA and KBMI. Winds S-SW 6-10 kts this afternoon, becoming
light and variable this evening, then W 4-8 kts by 16Z.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT Sunday for ILZ066>068-071>073.

&&

$$

KEY MESSAGES...Copple
DISCUSSION...Copple
AVIATION...37