150
FXUS63 KILX 051056
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
556 AM CDT Sat Jul 5 2025

.KEY MESSAGES...

- Partly to mostly sunny skies along with hot and humid conditions
  will prevail again today across central and southeast IL.
  Isolated showers and thunderstorms (20-40% chance) are possible
  over the IL river valley later this afternoon and early evening.
  There is a marginal risk of severe storms for damaging winds
  over Knox and Stark counties late this afternoon into mid
  evening.

- A better chance of showers and thunderstorms develops after dark
  tonight into Sunday (30-60% chance) as a cold front slowly moves
  into central IL. Locally heavy rainfall, lightning and a few
  strong wind gusts are possible mainly Sunday afternoon and
  evening, and again Monday afternoon in southeast IL.

- Hot and humid conditions will prevail this 4th of July holiday
  weekend, with highs 90 to 95 today and upper 80s to around 90
  Sunday, with afternoon heat indices in the mid 90s to near 100
  degrees.

&&

.DISCUSSION...
Issued at 345 AM CDT Sat Jul 5 2025

Early morning surface analysis shows 1022 mb high pressure over
the mid Atlantic States and southern New England, and ridging
westward into the mid MS river valley and southeast IL. A cold
front was perched over the Northern Plains/upper Midwest from
central MN into southeast SD. Aloft a 590-592 dm 500 mb high
extended from Texas into the the Ohio river valley and southern
Great Lakes with a 592 dm 500 high centered over the lower Ohio
river valley. Patchy shallow fog noted in southern/se IL and into
parts of central/southern IN. Patches of high cirrus clouds over
the IL river valley, otherwise nearly clear skies over CWA at
predawn with more cloud cover west/nw of IL.

Another hot and humid summer day unfolding today over IL as skies
become partly to mostly sunny. Much of CWA will be dry again
today, though isolated convection possible by late this afternoon
and early evening over the IL river valley where air mass to be
more unstable and closer to approaching cold front moving se into
central parts of IA/WI by early evening. SPC Day1 Outlook
continues marginal risk of severe storms for damaging winds over
Knox and Stark counties from late afternoon into mid evening.
Locally heavy rains also possible this evening over IL river
valley as PW values increase to 2-2.3 inches. WPC Day1 ERO has
marginal risk of excessive rainfall nw of IL river this evening.
Highs today of 90-95F with afternoon heat indices in the mid 90s
to near 100F. SSW winds increase to 10-15 mph with gusts 18-25 mph
west of I-57 by afternoon, so providing some relief from the
heat.

Cold front to push into nw parts of MO and IL by 12Z/7 am Sunday
and convection chances to increase to 30-50% west of I-57 during
tonight after dark, with slight chances along I-57 overnight. Cold
front to slowly move into central IL by late Sunday with better
chance of convection over central and southeast parts of CWA, se
of the IL river by Sunday afternoon. SPC does not have marginal
risk over IL on Sunday afternoon/evening, though a few cells could
have gusty winds. WPC day2 ERO has marginal risk of excessive
rainfall se of the IL river on Sunday afternoon/evening. Highs
Sunday in the upper 80s over central IL (mid 80s over Knox and
Stark counties) and lower 90s in southeast IL and near the IN
border. Heat indices peak in the mid to upper 90s on Sunday
afternoon with tropical dewpoints in the low to mid 70s.

Cold front slowly moves into southeast IL on Monday. Convection
chances linger from I-72 south on Monday with best chances in
southeast IL on Monday afternoon (30-50% pops), where WPC Day3
ERO has marginal risk of excessive rainfall southeast of I-70.
Highs Monday in the mid 80s central IL and upper 80s in southeast
IL. Isolated convection possible until dusk Monday evening in
southeast IL, otherwise a dry period expected over central IL
Monday night and Tue morning. The frontal boundary lifts back
north into central IL Tue afternoon and have isolated convection
possible Tue afternoon especially south/sw of I-74. Very warm and
humid Tue with highs in the upper 80s to around 90F and afternoon
heat indices in the low to mid 90s. Isolated showers and
thunderstorms possible Tue night and Wed morning, then have chance
pops Wed afternoon into Thu afternoon, with highest pops 40-50%
Wed and Thu afternoon when airmass most unstable. The front to
linger near central/southern IL Wed-Fri keeping daily chances of
convection around along with humid conditions. Forecast models
differ with features during mid/late week so confidence is low on
timing and chances of convection. There is some agreement on
cutoff upper level low moving into the upper Midwest and western
Great Lakes Fri night and Saturday and trof digging down into IL
which would keep unsettled wx pattern going. Though this pattern
would also bring more seasonable temperatures without oppressive
heat wave we experienced from June 21-30th.

07

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 556 AM CDT Sat Jul 5 2025

Fairly quiet much of the period, with VFR conditions and winds
picking up to around 10-12 knots by late morning. Potential for
thunderstorms at the western terminals has been slowing a bit, and
will only include KPIA/KSPI in a PROB30 group for the evening.

Geelhart

&&

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

$$