628
FXUS63 KILX 292309
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
609 PM CDT Sat Aug 29 2026

.KEY MESSAGES...

- A late season heat wave is forecast to impact central and
  southeast IL for the upcoming week starting Sunday. Daily
  heat indices are projected to reach around 100 Monday
  afternoon, 100-105F Tuesday through Thursday and upper 90s to
  around 100 Friday.

- Precipitation chances are low for the next several days,
  though an active storm track is forecast just to our north
  for much of next week.

&&

.DISCUSSION...
Issued at 330 PM CDT Sat Aug 29 2026

Current Conditions & Synoptic Overview:
A broad ridging pattern sits over the central CONUS aloft, with
a mid-level shortwave impinging into the zonal flow along the
northern periphery of the ridge across Iowa and northern
Illinois. Remnant showers associated with this shortwave have
slowly pushed into northwestern Illinois as the day has
progressed, but organization and intensity continues to wane as
showers become removed from their forcing mechanism.
Additionally, the 12Z ILX sounding indicates the presence of an
EML, and any precip that falls will need to fall through
15,000ft of dry air without evaporating to reach the surface,
which appears rather unlikely (5-10% chance along and north of
I-74, <5% elsewhere). However, the system has brought widespread
high cloud cover to the area, which will linger into tonight.
The evaporative cooling from the virga should also permit 15-20mph
wind gusts to mix down to the surface this afternoon.

Otherwise, temperatures will reach the low to mid-80s this
afternoon, with the warmest temperatures in areas furthest to
the south and west. Lows tonight fall to the upper 60s east of
I-55 and into the low 70s along and west of I-55.

Warm Front Raises Temps Sunday:
As the 850mb high pressure sags south and east, strong
southwesterly flow from the Plains advects warmer temperatures
into the region late tonight into Sunday morning. The warm front
pushes to the north of the area by late morning, increasing
temperatures into the low to mid-90s Sunday afternoon and
bringing heat indices into the mid- to upper 90s.

Low Rain Chances Sunday Morning:
As the warm front pushes through the area early Sunday morning,
the nose of the nocturnal LLJ may overlap with energy from
another, slightly stronger shortwave that rides along the top of
the ridge again tonight, which would allow some scattered
convection to develop. However, the moisture that will ride
along the southerly wind will lag behind the initial front a
bit, so there will still be a significant layer of dry air in
the low-levels that precip will need to overcome before rain
reaches the ground. For that reason, PoPs between 7-10AM max out
between 10-25%, with the best chances being furthest north of
the I-74 corridor.

Hot All Week:
Main weather story continues to be the incoming heat that will
last through the duration of the week. Ensembles remain in good
agreement that temperatures will increase into the mid- to upper
90s on Sunday and remain there through at least Wednesday as the
ridge stays parked over the southeast US. Temperatures approach
triple digits Tuesday and Wednesday, with the probability for
heat indices >100 degrees starts creeping up in the far southern
counties on Tuesday (35-60%) per the LREF, further increasing to
widespread 30-75% on Wednesday and remaining at 30-60% on
Thursday. In addition to warm daytime highs, the low temperature
overnight only drops into the mid- to upper 70s on Tuesday and
Wednesday. The long duration of anomalously warm temperatures
for early September and lack of overnight relief starts pushing
the area into Major (Level 3 of 4) to Extreme (Level 4 of 4)
Heat Risk by mid-week, and remains elevated as the holiday
weekend approaches.

Should Stay Dry Most of the Week:
Central Illinois should remain near enough to the center of the
ridge in zonal flow to avoid most of the nocturnal MCS activity
that will result from repeated shortwaves riding along the
northern edge of the ridge, but low (<5%) PoPs in the far
northern reaches of the CWA could increase if the
strength/amplitude of the ridge is being overdone in the global
models or if the undercutting shortwaves come in a little
stronger than what is currently being modeled. By Wednesday and
Thursday, guidance indicates that the ridging over the southeast
US starts breaking down, opening the door to increased rain
chances Thursday and beyond.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 606 PM CDT Sat Aug 29 2026

VFR conditions expected the next 24 hours, with ceilings
generally in the 15kft range or higher. Southeast to south winds
will remain in the 10 knot vicinity through Sunday, with some
gustiness in spots toward midday. A low level jet is expected
to ramp up to the west this evening, but current projections
keep it no closer than the IA/IL border, thus no LLWS mention at
KPIA appears needed at this time.

&&

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

&&

$$

KEY MESSAGES...Camden/WFO SGF
DISCUSSION...Camden/WFO SGF
AVIATION...Geelhart