977
FXUS63 KILX 231049
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
549 AM CDT Sat Aug 23 2025

.KEY MESSAGES...

- There is a 20% chance for visibilities less than 1 mile in
  patchy fog this morning near and south of roughly I-72. Drivers
  and pedestrians should use extra caution, leaving extra time for
  the morning commute.

- After isolated showers and storms today (20% chance),
  conditions will turn dry and seasonably cool with overnight lows
  dipping into the upper 40s to low 50s by next work week.

&&

.DISCUSSION...
Issued at 116 AM CDT Sat Aug 23 2025

***** PATCHY FOG THIS MORNING *****

At 1am, temperatures had fallen into the mid 60s across central and
southeast IL, with dewpoints generally running 1-4 degrees lower.
It`s difficult to tell how much more temps will drop in any given
location as scattered mid to high clouds move overhead. Where any
breaks in clouds occur, radiational cooling may be sufficient to
result in patchy fog. Already, brief visibility drops to 5 and 3
miles have been observed at Paris and Springfield, respectively.
HREF probabilities for sub 1/2 mile visibilities are highest (at
15-30%) near and south of roughly the I-70 corridor, however a
few recent iterations of the HRRR suggests dense fog may develop
as far north/west as I-72/Jacksonville. Whatever fog does manage
to develop should quickly "burn off" with surface heating after
sunrise, with visibilities > 6 miles area wide by 9am.

***** ISOLATED STORMS THIS AFTERNOON *****

This fog and low stratus will give way to scattered cumulus clouds
today, particulary near and east of roughly I-55 where HREF mean
brings MUCAPEs to 1000+ J/kg ahead of a front. The instability,
coupled with 20-30 kt effective bulk shear, suggests the
reflectivities depicted by several CAMs near and south of roughly
the I-72 corridor will carry a risk of lightning, so we matched
thunder to PoPs (20%) in the forecast there. This activity will be
moving quickly, so one shouldn`t expect much in the way of rain even
if they do get a shower/storm; HREF LPMM is only showing up to
around a quarter inch of rain with the heaviest cells. Outside of
these showers and storms, it will feel like August ahead of the
front with temps in the mid 80s and dewpoints approaching 70 in
spots, then more autumn-like behind it this evening with
dewpoints falling into the 50s and northwest winds gusting to
20-25 mph.

***** COOL AND DRY NEXT WEEK *****

By Sunday, a drier and cooler airmass will have arrived across all
of central and southeast IL. High temperatures Sunday will be mainly
in the mid to upper 70s, while on Monday the forecast has highs
barely touching 70 near and north of a roughly Rantoul to Macomb
line. Monday and Tuesday nights, surface high pressure will favor
lows in the low 50s to upper 40s; NBM probabilities for sub 50
degree lows is 20-40% (highest chances west) and 30-50% (highest
chances east) each night, respectively. All the while, the dry
airmass should keep the area precipitation-free with less than a 10%
chance for rain each day through Thursday.

Bumgardner

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 549 AM CDT Sat Aug 23 2025

A boundary dropping southeast out of Iowa has sparked a few
showers, which have a small chance of impacting PIA in the next
couple hours but model guidance suggests will break up before
reaching any other terminals. Additional showers and perhaps
thunderstorms may develop along the front later this afternoon,
with DEC and CMI having the highest chances (around 20%). Because
the probability of lightning is less than 30%, we have not
included a prob30 group to highlight this potential; if those
storms impact either airfield, the timing would be roughly 20-24z.
Southwest winds will veer to northwesterly with the first boundary
this morning, and then strengthen this afternoon with gusts
approaching 20 kt.

Bumgardner

&&

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

$$