135
FXUS63 KILX 071931
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
231 PM CDT Fri Aug 7 2026

.KEY MESSAGES...

- Typical summertime heat and humidity will return to central
  Illinois early next week. Heat index readings will peak at or
  above 100 degrees across all or parts of the area Sunday
  through Tuesday.

- Clusters of thunderstorms will track across the Midwest over
  the next several days. At this time, it appears the most
  likely time frame for storms in central Illinois will be late
  Saturday night into Sunday morning...then again Tuesday night
  into Wednesday.

&&

.DISCUSSION...
Issued at 231 PM CDT Fri Aug 7 2026

A cold front currently extending from Minnesota to Nebraska will
sag southeastward this evening, triggering scattered thunderstorms
across Wisconsin and Iowa. A few of these cells could potentially
spill into the N/NW KILX CWA in a weakening phase from late
evening through the overnight hours. Have included low chance
PoPs (20-30%) along/north of a Rushville to Bloomington line
accordingly. The front will continue southeastward on Saturday,
but will eventually become parallel with the upper flow and
stall along the I-64 corridor. A weak bubble of high pressure
behind the front will ensure a dry day for most of central
Illinois, with just a slim chance (20%) for a stray shower/storm
near the boundary along/south of I-70 during the afternoon.

As a nocturnal low-level jet streak strengthens across the
Plains, a cluster of thunderstorms is expected to form along the
trailing end of the boundary Saturday night, then track E/SE
toward central Illinois overnight into Sunday morning. There is
still wide variation among the 12z models with the FV-3/RRFS
both focusing convection further north across Wisconsin...and
the HRRR/ECMWF/ICON favoring a more southerly position over
eastern Iowa/northern Missouri by 12z Sun. While the details are
not yet fully settled, confidence is growing that a cluster of
storms will impact at least parts of central Illinois. Have
therefore focused highest PoPs (40-50%) along/north of the I-72
corridor late Saturday night into Sunday morning. Once any
morning storms depart, the afternoon will be largely dry and
decidedly more humid as dewpoints climb into the middle to upper
70s. With temperatures well into the 80s to near 90 degrees,
heat index values will peak in the upper 90s to around 100
degrees by Sunday afternoon.

Even hotter conditions are expected on Monday/Tuesday as upper
ridging shunts the bulk of the convection just north of the KILX
CWA from northern Iowa across Wisconsin/northern Illinois. Will
need to keep a close eye on the situation as mesoscale details
become fine-tuned, but for now it appears both days will be
mostly dry with highs in the 90s and heat index readings
flirting with Heat Advisory criteria (105 degrees).

All model guidance agrees that a stronger short-wave trough will
push a cold front southward into central Illinois Tuesday night
through perhaps the end of next week. Nocturnal convection will
likely blossom along the boundary Tuesday night into Wednesday
morning, providing all of central and southeast Illinois with
high PoPs (60-80%).

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1251 PM CDT Fri Aug 7 2026

A robust Cu-field has developed across central Illinois early
this afternoon with ceilings ranging from low VFR to MVFR. Based
on satellite trends, have opted to carry a TEMPO group for MVFR
ceilings at all sites except KPIA through 20z. After that, both
NAM and RAP forecast soundings suggest the diurnal clouds will
scatter...followed by mostly clear skies through the evening.
High clouds will be on the increase overnight as a cold front
approaches from the northwest: however, it appears lower clouds
and/or showers will largely stay northwest of the Illinois
River late tonight. Winds will veer to the SW but remain under
10kt this afternoon, then will veer to W/NW as the cold front
slowly edges into the region by Saturday morning.

&&

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

&&

$$

KEY MESSAGES...Barnes
DISCUSSION...Barnes
AVIATION...Barnes