226
FXUS63 KILX 271948
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
248 PM CDT Sun Sep 27 2026

.KEY MESSAGES...

- Quiet and tranquil weather continues across central and
  southeast Illinois through Tuesday night, with seasonable high
  temperatures in the mid to upper 70s Monday and upper 70s and
  lower 80s Tuesday. Patchy shallow ground fog possible late
  tonight and early Monday morning northeast of I-74 and near
  the Indiana border.

- Widespread showers and a few thunderstorms are expected
  Thursday through Friday over central and southeast IL. The
  exact location of the heaviest rainfall and accumulations
  remain highly uncertain, and current NBM forecast amounts
  have come down to between 1.5 and 2 inches.

&&

.DISCUSSION...
Issued at 230 PM CDT Sun Sep 27 2026

A blocky upper level pattern continues across the country next
few days with strong cutoff low/trofs over the Mid Atlantic
coast and West coast early this week and upper level ridge in
between over the nations heartland. Quiet/nice early fall
weather will likely continue across central/se IL through at
least Tuesday night and may even extend into Wednesday as the
western upper level trof is slower to shift eastward into the
central Rockies/central high plains on Wed. More active pattern
evolves over the region Wed night into Friday as system in
western states moves into the Midwest with a frontal boundary
along with remnants of Polo affecting the area late this work
week.

Mid level convergence driven band of isolated to scattered
showers over eastern Iowa central/eastern MO, AR and west
central and far sw IL near MS river valley from near
Jacksonville and south and sw. Jacksonville airport picked up
0.13 inch rain this morning. Latest CAMs continue to diminish
these light showers next few hours over areas from Jacksonville
sw with dry conditions expected over area by sunset. Some of the
CAM members like HRRR, RAP and NAM3km show patchy fog (possibly
dense) developing from I-74 northeast and near the IN border
during overnight into early Monday morning. Lows overnight in
the upper 40s/lower 50s, coolest east of I-55 where less cloud
cover.

Upper level ridge builds into IL through Tue with temperatures
gradually warming up into mid to upper 70s Monday and mostly
lower 80s Tue (upper 70s over Knox and Stark counties). Lows in
the low to mid 50s Monday night, coolest in east central IL. Even
warmer on Wed with southerly flow with highs ranging from upper
70s by Galesburg to mid to upper 80s in southeast IL. We have
20-40% chance of showers from Quincy to Bloomington north/nw on
Wed with isolated thunderstorms from Galesburg nw. Highs Thu
still in mid 80s in southeast IL while low to mid 70s from IL
river nw.

The strong upper level trof near the West Coast to shift
eastward into the central Rockies and central High Plains by Wed
while picking up remnants of Hurricane Polo with showers and a
few thunderstorms becoming more likely overnight Wed night over
the IL river valley and over rest of CWA on Thu, though
southeast IL may not see likely pops until Thu night/Friday.
Hurricane Polo with 125 mph winds forecast by NHC to track NE
into southern Baja of Mexico late Monday afternoon and weaken as
it moves across the Baja peninsula and reach the nw Mexican
coast late Mon night. Its remnants reach near El Paso Texas by
sunset Tue and its moisture likely to move into IL for the
Thu/Fri time period. NBM pops have lowered from 2-3 inches to
1.5-2 inches as the system appears slower moving in and and
faster moving out Friday afternoon/evening as upper level trof
opens up. Severe thunderstorm risk still appears low late this
work week though moderate to heavy rains still a risk as WPC
Day5 for Thu/Thu night has slight risk of excessive rainfall
over central IL and marginal risk in southeast IL.

A 1027-1030 mb high pressure settles into the western Great
Lakes Friday night and eastern Great Lakes by sunset Sat
bringing drier wx back to the area Fri night and Sat. Models
differ with handling next southern stream system early next
week with ECMWF much wetter over CWA on Sunday while GFS and GEM
models keep moisture south of CWA. NBM has 20-30% pops se of the
IL river on Sunday. Cooler more fall like temps return Friday
through Sunday with highs in the mid 60s to lower 70s and lows
in the low to mid 50s.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1230 PM CDT Sun Sep 27 2026

Canadian high pressure over Quebec Province will continue to
ridge into IL into Monday, providing fair wx/VFR conditions over
central IL through 18Z/1 pm Mon with SCT-BKN mid/high clouds.
The exception will be across far west central IL where a weak
disturbance is bringing isolated to scattered light showers
today, but these should stay south and west of Jacksonville
(KIJX). Light NE or variable winds around 5 kts or less to
prevail next 24 hours. Patchy fog could develop ne of I-74 late
tonight/early Mon morning but kept mention of fog out of I-74
taf sites (PIA, BMI, CMI) for now as latest HRRR and RAP13 runs
keep vsbys restrictions northeast of these airports.

&&

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

&&

$$

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