862
FXUS63 KILX 181829
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
129 PM CDT Tue Aug 18 2026

.KEY MESSAGES...

- While heavier rain with an overnight thunderstorm complex
  stays to our south, periods of showers and a few thunderstorms
  are expected late tonight into Wednesday morning.

- A persistent northwest flow will keep temperatures and
  humidity levels in check the next several days, with highs in
  the upper 70s to lower 80s common.

&&

.DISCUSSION...
Issued at 125 PM CDT Tue Aug 18 2026

A general northwest upper flow will prevail over the next
several days, as a large low over northern Ontario drifts east
and ridging builds west of the Rockies. This will keep any sort
of hot weather at bay, with high temperatures generally in the
upper 70s or lower 80s into early next week.

Morning high-res models develop an MCS over northwest Missouri/
northeast Kansas this evening, near the nose of a 700 mb jet.
Morning high-res guidance is in decent agreement with the core
of the MCS passing just to our south, though the NAM-Nest has it
scraping as far north as Jacksonville and Springfield. Remnants
of this MCS should reach southeast Illinois early Wednesday
morning. Ensemble guidance suggests the heaviest rain staying
south of our area, though locally heavy rain south of I-70
isn`t out of the question as precipitable water values in that
area will be close to 2 inches. By daybreak, a shortwave will
be dropping south into central Illinois, though loitering until
a more substantial wave sweeps across early Thursday. This
second wave will bring a period of dry conditions for late in
the work week.

As the ridge builds across the western U.S. late this week,
another weak wave will sweep across the Midwest, prior to a
deep upper trough digging to our east. This may bring a few
showers and thunderstorms Friday night into early Saturday.
However, any substantial rain chances should stay to our west
late weekend into early next week, with surface high pressure
dominating the region.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1214 PM CDT Tue Aug 18 2026

Main aviation concern will be developing closer to 10-12z, as
ceilings deteriorate ahead of a thunderstorm complex that will
track across Missouri into southern Illinois. Best chances of
any thunder at the terminals will be at KSPI/KDEC between
10-15z. By 13-14z, ceilings generally will be in the 3500 foot
range, though probabilities of dropping to MVFR levels at
KPIA/KBMI are around 40-50%.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

KEY MESSAGES...Geelhart
DISCUSSION...Geelhart
AVIATION...Geelhart