496
FXUS63 KILX 281113
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
613 AM CDT Tue Jul 28 2026

.KEY MESSAGES...

- In the wake of the passage of a cold front early this morning,
  drier air will slowly filter into the region today, with more
  substantial lower dew points arriving tonight into Wednesday
  night.

- A cutoff low moving near IL late this week, will likely bring
  periods of showers and a few thunderstorms Friday into this
  weekend. LREF has a 30-40% chance over 1 inch of rain Fri/Sat
  over central IL while NBM has a 40-60% chance over 1 inch
  rain.

&&

.DISCUSSION...
Issued at 340 AM CDT Tue Jul 28 2026

The 08Z/3 am surface map shows a weak cold front near I-72.
Isolated convection along it over our far northern CWA late Mon
evening had dissipated a few hours ago and just some patchy
cumulus clouds along and se of the boundary. Warm temps in the
upper 70s to around 80F except 74 at Macomb and Galesburg. Moist
dewpoints in the mid to upper 70s in central IL, though lower
70s arriving nw of the IL river and around 80F dewpoints se of
I-70.

Latest CAMs push cold front across southeast IL by mid morning
and reaching near the Ohio river by 15Z/10 am. Consensus of
models keep our CWA dry with passage of cold front with winds
turning northerly and slowly bringing in cooler and less humid
air. MCS over southeast Nebraska to weaken as it moves se
across MO today keeping its convection west/sw of IL. Highs
today in the mid to upper 80s (coolest from I-74 ne) while
dewpoints settle into the upper 60s/lower 70s during this
afternoon. Afternoon heat indices peak in the mid to upper 90s
from Springfield to Effingham to Robinson sw with heat indices
topping 100F just south of CWA where heat advisory continues
today for Marion, Wayne, Edwards and Wabash counties. Variably
cloudy today with some passing smoke at higher levels from
wildfires over the Pacific Northwest/northern Rockies. The near
surface smoke models show some diffuse smoke passing southward
behind cold front during this morning though current
observations over IL and nearby states not showing much
restriction to visibilities.

Mostly clear skies expected tonight with ample sunshine Wed as
weak high pressure 1016-1018 mb settles down over WI and IL by
Wed morning. Comfy lows overnight and Tue night in the lower 60s
(near 60F in east central IL) with highs Wed in the low to mid
80s. Highs Thu in the mid 80s with weak surface high pressure
staying near IL with light winds. Slight chance of light rain
showers late Thu night over western CWA otherwise much of CWA
remains dry thru Thu night. Seasonable lows Thu night in the mid
to upper 60s.

Medium range models continue to show a decent northern stream
short wave ridging over top of mid/upper level ridge over the
central and southern Rockies/Southwest States, that develops a
cutoff low near MN/IA Fri morning. This to likely spread showers
and isolated thunderstorms east/se over central IL by Friday
afternoon with highest pops (50-70%) from I-55 west/nw. We have
50-70% pops arriving over area Fri night and Saturday. WPC Day
4 ERO has a marginal to slight risk of excessive rainfall Fri
afternoon and Fri night, with the slight risk over western half
of CWA. WPC Day5 ERO has marginal risk of excessive rainfall
across IL Sat/Sat evening with slight risk in far se IL. SPC and
Machine Learning do not have any risk area for severe wx over IL
late this week as instability appears to be weak. Highs Fri in
the lower 80s (near 85F at Lawrenceville) and upper 70s to around
80F on Sat. The GEM models is quicker weakening and exiting
upper level low/trof se of IL by Sunday morning, though Ecmwf
and GFS models linger weak cutoff 500 mb low over the mid
MS/lower Ohio river valley on Sunday and Monday keeping chances
of showers around especially se of the IL river. If cutoff low
lingers nearby early next week, we would see cooler and wetter
conditions than currently forecast by NBM projections.

The Climate Prediction Center (CPC) 8-14 Day Outlook for Aug
4-10th has a 45-55% chance of above normal temperatures over IL
and precipitation trending near normal across the Prairie State.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 613 AM CDT Tue Jul 28 2026

Main aviation concern is with lower clouds advecting southwest
toward central Illinois. These roughly extend from KRFD-KHUF at
11z and are expected to reach the KBMI-KCMI vicinity over the
next 1-2 hours. A few hours of ceilings just above 1,000 feet
are expected in this area before they begin to erode and pull
eastward.

Winds have begun shifting to the north-northwest, and will be
becoming more northeast over the next several hours. Speeds
around 10 knots will prevail into early evening, before
diminishing from west to east.

&&

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

&&

$$

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