322
FXUS63 KILX 041835
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
135 PM CDT Fri Sep 4 2026

.KEY MESSAGES...
- Dangerous Heat Saturday: Heat index values will reach to
  around 105 degrees again on Saturday. The Extreme Heat
  Warning has been expanded to cover all of central Illinois.

- Brief Weekend Relief: A cold front pushing south will bring
  slight less hot and humid conditions to northern areas Sunday
  and Monday, dropping highs into the mid-to-upper 80s. Southern
  areas will remain warmer in the low 90s.

- Heat Returns Next Week: The brief break in oppressive heat
  will be short-lived. Widespread 90-degree temperatures and
  triple-digit heat index values are forecast to return Tuesday
  and Wednesday.

&&

.DISCUSSION...
Issued at 130 PM CDT Fri Sep 4 2026

Central Illinois remains positioned along the edge of a strong
upper-level ridge with a Ring of Fire pattern resulting in daily
convective chances in the region, mainly to our north.
Convective outflow originating from the mesoscale convective
system that tracked from the Upper Midwest into the southern
Great Lakes region earlier has sagged into portions of northern
Illinois and will need to be monitored closely this afternoon
and evening. Thunderstorm development cannot be ruled out within
a strongly unstable (>3000 J/kg MLCAPE) but weakly sheared
(15-20 kt) airmass. The local area is largely devoid of any
notable synoptic scale forcing, though, thus a mesoscale forcing
mechanism is needed.

Meanwhile, temperatures continue to run well above normal under
the influence of the upper ridge. The 12Z ILX sounding once
again measured 850mb temps just over 22C which is well above the
90th percentile (18.6C) for early September. Deep mixing under
mostly sunny skies will allow temps to reach the upper 90s with
a few spots tagging triple digits. Heat indices will top out
between 100-110F again this afternoon and early evening with
minimal relief overnight as temps bottom out only in the mid
70s, around 15 degrees above the seasonal norms.

Over the weekend, the upper-level ridge axis retrogrades west
toward the central Great Plains and amplifies, while an upper-
level trough digs south across Canadian Maritimes and New
England setting up an Omega Block. This will transition central
Illinois into a northwest flow regime heading into the weekend.
At the surface, an expansive ridge over Ontario and Quebec will
expand south into portions of the Midwest pushing a backdoor
cold front into portions of central Illinois, roughly to near
the I-74 corridor. This front is trending a bit slower which now
leaves most of central Illinois with highs in the mid to upper
90s again Saturday with heat indices again in the 100-110 range.
With this in mind, have expanded the Extreme Heat Warning to
the remainder of the area Saturday.

For Sunday and Monday, high temperatures in areas affected by
the frontal passage are expected to drop from the 90s down into
the mid-to-upper 80s. Further south, elevated heat will persist,
but temperatures will ease slightly with highs in the low 90s.
Heat indices Sunday and Monday should top out in the 90s
areawide, providing brief relief from the more oppressive heat.
Any relief in the area will be brief, however. By Tuesday and
Wednesday, the upper ridge axis is forecast to expand back
eastward bringing a resurgence of widespread 90-degree
temperatures across the area with triple digit heat indices
possible again both days.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1221 PM CDT Fri Sep 4 2026

West to southwest winds will dominate today and tonight, then
shift northwesterly Saturday morning ahead of an approaching
back door cold front from the northeast. Very unstable
conditions are in place, but lack of forcing should keep the
local area primarily dry until the cold front moves through
after the current TAF valid period.

&&

.CLIMATE...
Issued at 1211 AM CDT Fri Sep 4 2026

Record high temperatures through Saturday:

Location       Fri 9/4     Sat 9/5
========       ========    ========
Bloomington    100/1925    103/1899
Champaign      100/1954    102/1899
Charleston      98/1925    102/1954
Danville       101/1954    102/1954
Decatur        103/1913    104/1954
Jacksonville   103/1899    104/1899
Lincoln        102/1954    103/1954
Olney          103/1954    106/1925
Paris          104/1954    105/1954
Peoria          98/2015    104/1899
Springfield    100/1954     99/1954

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Warning until 7 PM CDT Saturday for ILZ027>031-
036>038-040>057-061>063-066>068-071>073.

&&

$$

KEY MESSAGES...Deubelbeiss
DISCUSSION...Deubelbeiss
AVIATION...Deubelbeiss
CLIMATE...Geelhart