864
FXUS63 KILX 271918
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
218 PM CDT Mon Jul 27 2026

.KEY MESSAGES...

- Oppressive heat and humidity continues through early evening
  with heat indices peaking between 105 and 115 degrees.

- Multiple thunderstorm complexes will move across IL this
  afternoon/evening, presenting a conditional threat for severe
  weather. Damaging winds (60-70+ mph gusts) and heavy rains
  are a risk especially in eastern and southeastern IL this
  afternoon and early evening.

- A cold front will bring relief from the high heat and humidity on
  Tuesday, transitioning us back to near normal temperatures
  and humidity levels during mid week.

&&

.DISCUSSION...
Issued at 218 PM CDT Mon Jul 27 2026

Outside of the storm risk today, it has been very hot and humid
today. Heat indices have been around 100-105 so far but still have
time to increase to about 115 degrees in some spots. The Extreme
Heat Warning continues until tonight at 9 pm. If thunderstorms
materialize and move in during the afternoon and early evening, it
would cool temps/heat indices and would likely end the heat
headlines earlier than 9 pm. Beyond today, temperatures become more
seasonable and less humid with highs in the 80s and lows in the 60s
through next week.

Today`s forecast has been a doozy. The models haven`t been of the
greatest assistance recently with this round of convection. We have
an Enhanced Risk (level 3 of 5) for areas near and north of a Henry
to Marshall line and a Slight Risk (level 2 of 5) elsewhere for
today. Primarily this risk is for damaging winds, potentially
stronger than 70 mph, but there is also a 2% tornado risk for the
area within the Enhanced Risk.

Our 12z sounding shows MUCAPE over 5500 J/kg, effective shear of ~50
knots, and PWATs of nearly 2 inches. A shortwave is pulsing through
this afternoon across Illinois and Indiana, based off GFS 500 mb
vorticity. The storms currently over the Chicago-Land area may clip
eastern IL as it drops south into Indiana and they are evolving into
a damaging wind threat as it transitions to a linear mode rather
than supercellular. It is starting to trend towards areas west of I-
55 may not see any of the severe threat today. There may be some
showers/storms that direction but it looks like the main show will
remain east of I-55 this afternoon/evening. An additional wave may
move behind it that will also drop south, potentially riding the
IL/IN border, but could possibly be weaker in strength, based off
the HRRR. The HRRR`s 16z and 17z runs are picking up the active
convection well. The storms should have exited by 10 pm tonight.
Storms will be moving to the south-southeast at 30-40 mph this
afternoon/evening.

The next chance for showers and thunderstorms comes in on Friday
into Saturday as a shortwave moves through the area.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1233 PM CDT Mon Jul 27 2026

VFR conditions are expected through the 18z period. There is a
chance for strong storms later this afternoon into the evening
hours. Confidence in the location and timing of the storms is
low so opted for the PROB30 group for 21-01z. Heavy rain will be
accompanying any storms, so lowered visibility is possible if
they move through. The winds will be veering throughout the
period, becoming northerly by the morning.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Warning until 9 PM CDT this evening for
ILZ027>031-036>038-040>057-061>063-066>068-071>073.

&&

$$

KEY MESSAGES...Copple
DISCUSSION...Copple
AVIATION...Copple