199
FXUS63 KILX 261859
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
159 PM CDT Sat Sep 26 2026

.KEY MESSAGES...

- Expect mostly dry conditions and seasonable temperatures
  through Tuesday afternoon, though a few light showers are
  possible over west central IL into this evening.

- Heavy rainfall and localized flooding become the primary
  concern Wednesday through Friday as repeated rounds of rain
  move across central Illinois.

- NBM has a 30 to 50% chance of rainfall exceeding 2 inches from
  overnight Tue night through Friday night over central and
  southeast IL.

&&

.DISCUSSION...
Issued at 200 PM CDT Sat Sep 26 2026

An upper level blocking pattern continues across much of the
country, with IL nestled between a deep coastal low
(Nor`easter) tracking along the Mid Atlantic/New England
seaboard through Monday and a shortwave trough lifting north/NE
across the Great Plains toward the Upper Mississippi Valley.
Mid level convergence and moisture advection will support
isolated to scattered mainly light showers into this evening
over west central IL, primarily along and west of a Galesburg to
Springfield line. Areas further east are drier with dewpoints
of 45-50F from persistent gentle east to NE flow so this will
keep shower chances further west. The latest CAM runs keep
patchy fog near or northeast of Kankakee and Lafayette IN
overnight and over nw Iowa. Lows overnight range from lower 50s
in eastern IL (upper 40s possible from Champaign and Robinson
east/ne and upper 50s in cloudier areas from Galesburg to
Springfield west/sw.

Nice early fall weather should continue Sunday and Monday across
the area with persistent blocking pattern remaining with
Canadian high pressure continuing to ridge toward IL with light
east to NE winds. Western and sw CWA will continue to see more
mid level clouds than eastern IL where partly to mostly sunny
skies should prevail. Seasonable highs in the low to mid 70s
with lows Sunday night mostly lower 50s, but ranging from
around 50 in eastern IL and mid 50s over west central IL/MS
river valley.

The Nor`easter to weaken and start pulling away from the New
England Coast Monday night and Tue while high pressure ridge
settles into the Mid Atlantic Region giving a southerly flow of
a bit warmer air into IL. Highs Tue in the upper 70s to near 80F
with increasing clouds from the west during Tue afternoon ahead
of an approaching frontal boundary in the Central Plains. It
should be dry during daytime hours over CWA on Tue with chances
of showers and a few thunderstorms arriving over the IL river
valley Tue evening and over rest of central IL overnight Tue
night. Chances of showers and thunderstorms likely holds off
until Wed in southeast IL.

Repeated rounds of showers and a few thunderstorms appears
likely from overnight Tue night through Friday evening.
Very high PWATs of 1.5-2.25 inches from Wed through Friday along
with remnants of Hurricane Polo interacting with the frontal
boundary near IL Wed-Fri to support moderate to heavy rains at
times. NBM has 30-50% chance over over 2 inches of rain over
much of CWA during this time frame. Weak instability and wind
shear parameters to keep the severe weather threat low with
localized flooding the main concern. Latest extended models are
trending wetter during next weekend with another deep mid/upper
level trof moving into the Midwest.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1230 PM CDT Sat Sep 26 2026

VFR condtions are forecast to continue across the central IL
terminals through 18Z/1 pm Sunday. Broken to overcast mid level
clouds with bases of 7-12k ft to affect areas from PIA and DEC
west, and be most prominent at SPI next 24 hours. Northeast
airports of BMI and CMI may periodically see brief broken mid
level clouds but mainly more scattered mid/high clouds there.
Latest CAM runs like HRRR model keep isolated light showers
west/sw of central IL airports through this evening, though will
be closest to SPI airport. Canadian high pressure over eastern
Ontario and western Quebec provinces and ridging into IL through
midday Sunday to keep fairly light east to ENE winds 3-8 kts.

&&

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

&&

$$

KEY MESSAGES...07
DISCUSSION...07
AVIATION...07