956
FXUS63 KILX 132315
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
615 PM CDT Wed Aug 13 2025

.KEY MESSAGES...

- Widely scattered thunderstorms will continue through early this
  evening in southeast Illinois, followed by a stretch of drier
  weather through the weekend.

- Hot and humid conditions return Friday through the weekend with
  peak heat indices ranging from 100 to 105 degrees.

&&

.DISCUSSION...
Issued at 155 PM CDT Wed Aug 13 2025

...Scattered Storms in Southeast IL Today...

Surface analysis this afternoon depicts a somewhat washed out
cold front stretched from roughly Paris, IL westward to near St.
Louis. Dewpoints have been slow to drop behind the front with the
most notable airmass change west of I-55 where 1 pm dewpoints are
in the low to middle 60s. Moisture rich air remains in place out
ahead of the front, which will support a few isolated pop-up
thunderstorms through early this evening. SPC mesoanalysis shows
SBCAPE values around or over 2000 J/kg in this area, though shear
is very weak. Similar to previous days, storms will develop rather
quickly, but the lack of organization will keep impacts minor.
With that being said, slow storm motions and high PWATs could
result in locally heavy rainfall and gusty winds may occur as
storms collapse.

The cold front will settle south of here later tonight as high
pressure slides in behind it. Gentle northeast winds will send a
cooler and drier airmass southward overnight with lows expected to
bottom out in the low to middle 60s. Patchy fog may develop
overnight in west-central Illinois where radiational cooling will be
most prominent under surface ridging, but also in southeast Illinois
where dewpoints will be slower to fall and pockets of heavy rain
fell earlier in the day.

...Turning Hot and Humid by the Weekend...

Upper ridging begins to amplify over the central US later this week,
bringing an extended period of dry and hot weather through at least
the weekend. Temperatures will be warmest on both Saturday and
Sunday as mid-level heights quickly climb to around 590-595 dam. Air
temperatures on both those days look to peak in the low to middle
90s with heat indices ranging from 100 to 105 degrees.

The heat will be short-lived with temperatures falling back to near
normal values (middle 80s) by the early to middle parts of next week
as the ridge retreats back westward. Our next chance for
precipitation looks to hold off until Monday/Tuesday timeframe as a
series of upper shortwave troughs send a frontal boundary southward
into the Midwest states.

NMA

&&

.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 605 PM CDT Wed Aug 13 2025

Northerly winds will gradually veer to a southeasterly direction
overnight into Thursday morning, while remaining generally 5 kt or
less. Overnight, there is potential for fog given mostly clear
skies and these light winds. HREF guidance continues to highlight
areas along and near the IL River Valley, though there is enough
of a signal at SPI and BMI that MVFR visibility mentions were
added in TEMPO groups this forecast cycle. Any fog that develops
should quickly dissipate between 12-14z (7-9am), with a slim (20%)
chance of MVFR (or lower) ceilings as diurnal cu develops.
Otherwise, VFR conditions should be predominant with a few high
clouds spilling in tomorrow afternoon.

Bumgardner

&&

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

$$