041
FXUS63 KILX 051921
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
221 PM CDT Sat Jul 5 2025

.KEY MESSAGES...

- Scattered showers and thunderstorms will spread eastward into
  central IL this afternoon and evening and continue into Sunday
  (40-70% chance) as a cold front slowly moves into the area.
  Locally heavy rainfall, lightning and a few strong wind gusts
  are possible.

- Hot and humid conditions will continue Sunday south of I-72,
  with highs near 90 and afternoon heat indices in the mid 90s to
  near 100 degrees. More seasonably hot and humid conditions can
  otherwise be expected the next several days as a cold front
  brings slightly cooler conditions.

- Occasional periods of scattered showers and thunderstorms can be
  expected for the upcoming work week.

&&

.DISCUSSION...
Issued at 221 PM CDT Sat Jul 5 2025

A cold front currently draped from northern WI southwestward
through IA and KS will be the focus for weather development over
the upcoming couple of days. Showers and thunderstorms ahead of
this feature continue to progress toward west central IL this
afternoon, and should begin to move into the IL River valley late
this afternoon or evening, slowly spreading eastward toward the
I-57 corridor and weakening overnight. Instability/CAPE will be
modest this evening, as high as 1000-2000 J/kg west of the IL
River, although deep layer shear will be under 20 kts. The most
favorable area for locally damaging wind gusts looks to be around
Knox and Stark Counties where SPC has a Marginal Risk for severe
storms designated. With precipitable water values potentially
exceeding 2 inches ahead of the front and slow storm motions,
locally heavy rainfall is a possibility. HREF ensemble
precipitation maximum depicts isolated 2-3 inch rainfall
accumulations, and WPC depicts a Marginal Risk for excessive
rainfall beginning in west central IL this afternoon, and
continuing through Monday for precipitation associated with this
front. Nevertheless, precipitation will be scattered and showery,
and average rainfall amounts through Sunday appear they will be
under a half inch. 1-hour Flash Flood Guidance values are around 2
inches.

As the front progresses into central IL Sunday, storms should re-
intensify with daytime heating, and CAPE values of 1000-2000 J/kg
with continued weak shear look to characterize the environment.
Again, locally heavy downpours in slow moving storms look to be
the main weather concern.

The front looks to stall out near southern portions of the
forecast area Monday, shifting rain chances mainly south of I-72.
As the work week progresses, a series of upper level waves should
move through the area in a weak zonal flow pattern, promoting
occasional scattered showers and thunderstorms. Exact timing
remains uncertain at this time for most of the week.

Temperatures will begin to trend downward slightly on Sunday with
the frontal zone, cloudy conditions and scattered showers over
the area. Highs look to range from 85 in Galesburg to 93 in
Lawrenceville. The work week looks to be characterized by
seasonably hot and humid weather for the week, with daily highs
from mid 80s to around 90, and lows mid 60s to around 70.

37

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1209 PM CDT Sat Jul 5 2025

Scattered showers and thunderstorms will shift eastward into the
central IL terminals tonight, although becoming weaker and more
scattered as they move into the area. A few MVFR cigs/visbys are
possible in storms, however general conditions are expected to be
VFR. At this time, probability of occurrence at terminals is
generally too low to mention thunderstorms, except for at KPIA
01Z-05Z where PROB30 for TSRA and MVFR conditions is included in
the 18Z TAFs. Otherwise, have included a period of VCSH for most
likely time periods for nearby shower activity. Nevertheless,
indications from model forecasts with this slow moving frontal
zone are that shower/thunder activity can`t be completely ruled
out any time prior to 18Z once activity begins. Winds SSW 10-15
kts with gusts to around 20 kts this afternoon, decreasing to 5-10
kts after 00Z, then beginning to shift more westerly by 18Z.

37

&&

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

&&

$$