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FXUS63 KILX 252322
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
622 PM CDT Sat Jul 25 2026

.KEY MESSAGES...

- Oppressive heat and humidity return Sunday and Monday with
  heat indices peaking between 100 and 110 degrees.

- Severe weather probabilities increase Sunday into Monday with
  Monday presenting the most favorable convective window ahead
  of an approaching cold front.

&&

.DISCUSSION...
Issued at 240 PM CDT Sat Jul 25 2026

Lingering cloud cover has held temperatures down several degrees so
far today with 2 pm readings ranging from the low 70s to near 80
degrees. Clouds will slowly erode from west to east through early
evening, though temperatures have been further reduced with highs
through the remainder of today peaking in the low 80s in western IL
and middle to upper 70s in eastern IL. After a brief break from the
low clouds this evening, strong warm air advection ahead of an
approaching warm front will bring another period of low stratus
overnight into Sunday morning as moisture gets trapped beneath a low-
level inversion. Pockets of lower visibility are also possible with
a low to medium chance (20-40%) for dense fog.

Mid-level heights rise heading into Sunday as the upper ridge
amplifies over the west-central US, sending 20-25C 850 mb
temperatures into the middle Mississippi Valley. Surface
temperatures will surge into the upper 80s to low 90s on Sunday, and
then the low to middle 90s on Monday. Dewpoints in the upper 70s to
80 degrees will equate to heat indices of 100 to 110 degrees the
next two days with Monday being the hottest. A Heat Advisory remains
in effect for counties west of I-57 Sunday afternoon through Monday
where confidence has remained highest in criteria being met (heat
index 105 degrees). An expansion eastward may be needed for some on
Monday.

One complicating factor to the heat is convection and cloud cover.
Central Illinois is positioned on the eastern periphery of the upper
ridge, making us a prime target for northwest flow/shortwave trough
activity. Our first opportunity comes during the day on Sunday
if the wave is strong enough to overcome our capping inversion.
Additional opportunities exist Sunday night through Monday night
as a couple more shortwaves and an approaching cold front serve
as our forcing mechanisms. However, placement and timing of
activity remains highly uncertain with CAMs providing little
help. Any storms that do develop will have the potential to
become severe as they move through an environment characterized
by strong instability (3500+ J/kg SBCAPE) and sufficient
vertical wind shear (~30 kts). Hazards with any severe storms
would be damaging winds, large hail, and heavy rainfall.

Temperatures and dewpoints drop closer to seasonal normals for the
middle to end of the week behind a cold front. Northwest flow
remains positioned aloft through the upcoming week and may open the
door for occasional precipitation opportunities through next
weekend. However, details remain uncertain.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 622 PM CDT Sat Jul 25 2026

Lingering MVFR cigs are expected for a few hours from KBMI-KDEC
eastward this evening, then VFR conditions are expected for a
few hours as decreasing cloud cover moves in from the west.
However, cigs are expected to lower again, along with patchy fog
as a warm front edges closer from the southwest. Guidance points
to lowest cigs and vsbys northeast of KSPI, generally reaching
IFR conditions by around 09Z, while conditions at KSPI should
stay MVFR or better. Improving conditions in the late morning
should yield VFR conditions by around 18Z. Chances for
thunderstorms are too low for mention in TAFs, however decaying
thunderstorms from storms currently in SD could impact the area
after 12Z if they hold together, so this will have to be
watched. Winds generally light and variable to S 4-8 kts through
the period.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon Sunday to 9 PM CDT Monday for
ILZ027>031-036>038-040>044-047>054-061.

&&

$$

KEY MESSAGES...NMA
DISCUSSION...NMA
AVIATION...37